In 1928, the route was under construction from Laurel Hill Road to Flatwoods Road and Nichols Hill Road to current PA 201 and completed the following year.  In 1929, the route was moved from Montour Street, Ewings Mill Road, Forest Grove Road, Pine Hollow Road, and Broadway between Coraopolis and McKees Rocks to the current alignment.  On May 13, 1929, Allegheny County Commissioner Joseph G. Armstrong officiated the ceremony which officially kicked off work on Saw Mill Run Boulevard.  Commissioner E. V. Babcock, Pittsburgh Mayor Charlres H. Kline, Council President James F. Malone, Councilman John S. Herron, and Henry Meuschke, a Castle Shannon resident who advocated for the project as far back as 1910, were in attendance for the ground breaking.  The project was funded by the 1928 "City Beautiful" bond issue, which was to finance other roadways such as Ohio River, Allegheny River, and Mosside boulevards.

In 1930, the route was paved from current PA 201 to current PA 136.  Also that year, the first section of Saw Mill Run Boulevard opened from Brownsville Road to the Liberty Tunnel.  The most challenging part of construction was the PA 88 intersection where seven individual roads intersected as well as the convergence of Clairton Run Creek and Saw Mill Run.  The designation was moved off Brownsville Road and Arlington Avenue onto the new highway and through the tunnel to the P. J. McArdle Roadway to keep the route complete.  In 1933, the rest of it to Woodville Street opened and the designation placed on the new boulevard.  In 1934, the section from Desiderio Boulevard to West Elizabeth was under construction and opened the following year.

In 1946, the route was moved off Taggart Road in Beaver County.  In 1949, construction began on a bypass west of Perryopolis from Star Junction to Wickhaven, and was widened from PA 201 to Star Junction.  The bypass opened in 1950.

Construction on the West End Bypass began in October 1949; however, it had its start a decade earlier.  Robert Moses, New York City planner extraordinaire, had been hired by Pittsburgh to untangle traffic as well as he had done in "The Big Apple."  This was one of his ideas and priced at $900,000 which was approved in February 1941.  The onset of World War II delayed the project, and by the time it was revised, the cost had jumped to $3 million.  It took nearly a year to blast and remove one million cubic yards of material needed to clear its right-of-way on the side of Mount Washington.  Outside of that, another challenge Harrison Construction Company faced was building a ramp from Steuben Street.

In 1951, the West End Bypass opened to traffic from the Penn-Lincoln Parkway to PA 837.  However, the PA 51 designation still followed Woodville Street and Wabash Street to the West End Circle until 1955.  In 1953, the designation was moved out of Darlington onto a new alignment south of town.

Construction began in the lat 1950s on the East Rochester-Monaca Bridge spanning the Ohio River, which opened in 1959 as a toll bridge.  Tolls were removed in 1973.

Work to widen and install a median began in Wickhaven and at PA 201 in 1958.  A median was installed in 1958 between Braden Road and PA 251.  The following year medians were installed between Star Junction and north of Uniontown at the US 119 interchange.

A median was installed in 1960 between PA 201 and PA 48.  In 1961, construction started on a new alignment from I-70 to PA 201, and opened the following year.  A median was installed in 1962 from I-70 to Wickhaven.  In 1967, the rest from Wickhaven to PA 201 was done.

In 1976, the route was changed to its current alignment between Stoops Ferry and Monaca.  Previous to that, it turned onto Narrows Run Road, then Brodhead Road to PA 18 and back to its current alignment in Monaca.  Previously PA 51 crossed the Rochester-Monaca Bridge along with PA 18, but with the tolls removed from the East Rochester-Monaca Bridge and it taken over by the state, the route was designated across that span.

Deterioration was beginning to cause issues for the Elizabeth Bridge in 1982.  In February of that year, PennDOT closed one of the southbound lanes and then two months later, implemented a five-ton weight limit.  PennDOT District 11 bridge engineer, W. G. "Jerry" Johnson, warned that the deterioration could easily spread to the northbound side if repairs were not made quickly.  Conn Construction Company of New Castle won the job with a bid of $53,900.  The problem happened when the cap of a concrete land pier on the West Elizabeth side began to crack and crumble, which caused the bridge to drop 1.5 inches.  Work to repair the pier cap, replace the expansion bearings, and fix the expansion dam began in July 1982 and finished later that year.  Three years later, it would undergo a full rehabilitation.

Tragedy struck on February 16, 1983 when a rockslide took place at 1:45 PM affecting the northbound lanes between Woodruff Street and Crane Avenue.  It happened 10 minutes after workers had set off 17 small ammonia nitrate charges to clear rocks off the slopes along the northbound side.  Ram Construction Company of Canonsburg had a contract with the City of Pittsburgh to perform the work but sub-contracting the blasting to Controlled Blasting, Inc. of Zelienople.  The city hired them after falling rock closed the right northbound lane in April 1982.  Workers had stopped traffic on either side of the slope when the blasting occurred at 1:33 PM; however, they let traffic through when it appeared that no additional rocks were falling.  The blasting may have loosened mud behind a boulder just enough to make it fall to the roadway below.  Norman Flint, a University of Pittsburgh professor in Geology, speculated that ice could have formed in cracks in the sandstone and the warm weather that day, caused it to melt which loosened more rock.  "This is just what the project was supposed to prevent," said Louis Gaetano, Pittsburgh's Public Works Director.

In all, an estimated 500 tones of sandstone, landed first on top of the bulldozer being operated by Andrew Burgan of Finleyville.  He had managed to leap off of it when workers on the ledge shouted a warning, but the boulder landed on him after crushing the bulldozer, killing Burgan instantly on his 36th wedding anniversary.  The boulder also crushed a white Ford Pinto being driven Ronald Miller, who had just gotten married, purchased a house, and whose wife was expecting a baby at the end of April that year.  "I'm angry," said Mrs. Carla Miller.  "It's just so unfair."  The boulder also crushed the passenger-side of the cab of a Kroger tractor-trailer, throwing the driver, Robert Hilditch of North Royalton, Ohio.  Motorists ran to his aid after he landed on the pavement.  "It was just like something you see in the movies," said Gary Namiotka of the Southside, who was sitting in his car waiting to go past the slope when the landslide occurred.  Saw Mill Run Boulevard remained closed until the following afternoon.

Unrelated to the accident, Ram Construction had been beset by financial difficulties including nearly losing its insurance coverage in January 1983 for failure to pay its premiums.  It did file for bankruptcy protection on January 21, and would have lost it's insurance four days later.  US Bankruptcy Judge Joseph L. Cosetti fortunately ordered the coverage reinstated and instructed Ram to pay the premiums.  He modified that order on February 5 at the request of the insurance company for coverage to end at 11:59 PM on February 24.

In 1997, construction began on the interchange at the southern portal of the Liberty Tunnel, and opened to traffic on November 20, 1999.

Those who drive PA 51 knew all too well that the intersection at PA 88 and Maytide Street in Pittsburgh could be a nasty bottleneck.  Ideas for improving the intersection first came to light in March 1992 and right-of-way acquisition began in 1998.  However, PennDOT District 11 determined that the high cost of the project combined with the minimal congestion that it would alleviate did not warrant funding, prompting five alternatives to be studied between 2002 and 2004.  Costs for the alternatives ranged from $45 to $84 million, and again, the project was put on hold due to lack of funds.  The design was modified again and presented at a public meeting on October 4, 2010, with final design, utility coordination, and right-of-way acquisition begun shortly after.  The $19 million project began in August 2013 and will include replacement of five bridges, construction of a new bridge, upgrading signals, lighting, and sidewalks, installation of traffic cameras, as well as improving drainage and stream bank restoration.  Two jughandles were built:  one for northbound traffic to turn left onto PA 88 and Glenbury Street to eliminate the logjam of left-turning vehicles and a second for southbound traffic wanting to turn left at Ivyglen Street.  The projected was completed by the end of 2016.

A $31.3 million rehabilitation project began in October 2017 on the Elizabeth Bridge.  Improvements planned were replacement of the concrete deck and barriers, steel repairs, expansion dam replacement, bearings repairs, concrete substructure repairs, full painting, and drainage upgrades.  The bridge had to be closed temporarily on the night of September 26, 2019.  That afternoon, crews shifted the weight of the deck from the cables that regularly hold it in place to temporary metal brackets.  In doing so, a two-foot section of a bracket buckled.  Crews managed to shift the weight back to the cables that were scheduled to be replaced, and while conducting an emergency inspection Thursday evening, it was determined to close the bridge to traffic.  PennDOT, the contractor Swank Construction, and consulting engineers worked around-the-clock to design and install a secondary system which provided a redundant safety measure.  The bridge was originally closed indefinitely, but after the repairs were made, it was reopened to traffic again on the evening of September 27.

Construction began in 2010 to relocate the route onto a new alignment between US 1 and PA 926 just east of Longwood Gardens.  "Under the project, crews will relocate about 5,000 feet of Route 52 and widen 1,400 feet of 926 and 4,000 feet of Route 1.  We’re going to install traffic signals on Route 52 at 926 and at the new intersection with Route 1," said Pennsylvania Department of Transportation spokesman Charlie Metzger.  The $15.4 million project concluded in October 2011 and consisted of approximately one mile of new roadway, widening and reconstruction of US 1/Baltimore Pike with installation of a new traffic signal, and widening of PA 926/Street Road at the intersection of PA 52 with a new traffic signal replacing the former installation.  Cost for the project were covered largely by federal and state highway funds, but Longwood Gardens also foot the bill for study and design work, as well as the bridge over the pond that empties into Bennetts Run.  Acquiring the right-of-way for the new alignment was a mere exchange of land between PennDOT and the botanical garden.  The main reason for the relocation was that Longwood Gardens wanted to develop the land that the former route passed through and divided, as it formerly traversed what is now Webb Barn Lane and then intersected PA 926 from the southwest.  Also, congestion and numerous accidents occurred at the former intersection just outside the botanical garden.

In 1930, the route was paved from Stoyestown to Hollsople, Ashville to Frugality, and Brook to now SR 3011 was paved.  In 1931, the route was under construction from Gallitzin to Ashville and completed the following year.  In 1932, the northern terminus was moved from Reedsville to Potters Mills.  Also the section in Kantner was paved as well as from Blough to Landstreet.

In 1967, the northern terminus was moved from US 322 in Potters Mills to its current location.

The southern terminus is moved from the Maryland state line to US 219 in 1970.  Traversed Johnstown on Napoleon Street, Somerset Street, Franklin Street, Main Street and left via Frankstown Road.  Southbound traffic Adams Street, Bedford Street, and Vine Street.

In 2004, the entire route was placed on Center Street in its entirety in Phillipsburg, instead of splitting traffic between it and Front Street.

A new bridge on the route through Irvona was dedicated on July 19, 2012.  The new span, which cost $3.9 million, opened in late 2011 just 70 feet upstream from the original span.  The name of the bridge was chosen to memorialize a local victim from Clearfield County of the September 11 attacks in 2001:  Mary Ellen Tiesi Memorial 9-11 Bridge.  Ms. Tiesi perished in the South Tower of the World Trade Center in New York City.  PennDOT Secretary Barry J. Schoch said, "The tales of heroism from the tragic events that unfolded on that horrific day in 2001 have left their mark on all of us.  Ms. Tiesi is not just a Pennsylvania hero but also a national hero, and by dedicating this bridge in her honor and memory, her name will forever stand as a testament to courage and bravery."  Her uncle worked on the construction of the original span.

In 1930, the route was paved from the Mayberry Township line to the Susquehanna River, Mausdale to Hillside Road, and from Washingtonville to the current PA 44 intersection.  In 1932, the route was paved from Lorson Road to PA 554 and from Elysburg to Atlas.  In 1936, the route was moved off the current PA 44 alignment between Jersey Shore and Turbotville and the western terminus moved to US 15 at the Susquehanna Trail.  Ten years later it was moved beyond that point to its current location near Montgomery.

In 1961, the eastern terminus was moved from Ashland to Mausdale replacing the PA 45 designation and signed on Ashland Road between Mount Carmel and Ashland.  In 1966, the eastern terminus was moved from PA 642 in Mausdale to its current location using the old PA 45 alignment between Mausdale and Mt. Carmel and Ashland and Nesquehoning.

A median was installed in 1971 from Danville to Interstate 80.  In 1992, cracks developed south of Centralia, and eventually the highway was closed.  The road was shut down in early 1994.  In 1999, the route was changed to bypass Centralia after years of the underground mine fire taking its toll on the highway.  The route was changed to follow SR 2035, PA 901, SR 2042, SR 3002, and SR 4028 to rejoin its former route along PA 61.

In 1930, the route was moved from Iron Street, Walnut Street, and Main Street to Front Street, John Street, and Vine Street.  In 1932, the route was paved from Shady Plain to Jacksonville Road.

In 1951, construction began on a new alignment from Shearersburg to PA 356 and opened the following year.  In 1959, the highway was widened and a median installed on it from Leechburg Road to Melwood Road.

Until 1960, the route was came in on Johns Street and Vine Street into Johnstown.  Then the route was on Washington Street, Johns Street, Main Street eastbound, Vine Street to Roosevelt Boulevard westbound, and on Bedford Street.  In 1960, work began on the section from PA 601 to east of Rummel, which opened in 1961 and included widening and dividing from Geistown to PA 601.  Also in 1961, a new alignment from New Kensington to Leechburg Road opened and the designation moved onto it from going through Lower Burrell and Arnold on Locust Street, Freeport Road, and Leechburg Road to the current alignment.

In 1964, the eastern terminus was moved from Cessna to its current location.  In 1965, the route was moved onto the Johnstown Expressway from the Widman Street interchange to US 219 and down that expressway to Scalp Avenue when that section of expressway was completed.

In 1971, a new alignment opened from Vandergrift-Leechburg Road to Vandergrift.  Previously it continued on PA 356 to Labelle Vue Road, Holland Street, Longfellow Street, and Alternate PA 66.  That same year construction was extended from the Bedford Street interchange to Roosevelt Boulevard.  In 1972, the section from the Widman Street interchange to the Bedford Street interchange opened to traffic.  Construction finished on the section of Johnstown Expressway from Somerset Street to Dale in 1973, and with that, the designation was moved onto the new highway and Roosevelt Boulevard.

The Johnstown Expressway became a victim of the 1977 Johnstown Flood, when at 2:00 AM on July 20, runoff from Solomon Run cut the Widman Street exit ramp in half as well as washing out a section of the eastbound lanes just east of that interchange.  Sections of the westbound lanes in Scalp Level were undermined by the floodwater which caused part of the roadway to collapse.

When the final section of the Allegheny Valley Expressway between Exit 13 and Exit 15 opened in 1985, and PA 28 moved onto it from Freeport Road, PA 56's western terminus moved from that intersection across the New Kensington Bridge to the current terminus at Industrial Boulevard.

In 1997, the route changed from the path it took from Shady Plain to Homer City via West Lebanon and Edgewood to the current path.  The new route created several new multiplexes, with the most unusual with PA 156 from South Bend to Shelocta where that highway has its terminus.  The original route is not forgotten as it is named Old Route 56 Highway West in Indiana County where it is SR 3056, and in Armstrong County where it is SR 2056.

With PennDOT restructuring their 12-Year Transportation Program, two projects along PA 56 are now in jeopardy.  The first is the relocation of the alignment near Pleasantville in West St. Clair Township to eliminate the hairpin curve locally referred to as the “Peggy Westover Curve."  The section was studied in 1995 with bid letting in 2007, but now the project has moved into the reevaluate column.  The second project which would involve a realignment of the route in Johnstown's West End has been deferred.

A portion of hillside came crashing down onto the route in Johnstown on June 16, 2015.  "It’s an unfortunate incident, but given the landscape of around our city, is something that we have seen before and probably will see again," Johnstown City Manager Carlos Gunby said.  "But PennDOT and all of its resources are on it.  I’ve talked with them and they are working diligently to get this stretch of 56 open to reduce the impacts of the already highly trafficked and over surged areas due to the ongoing projects we have going on in the city."  The projects he was referring to were the Haynes Street Bridge replacement and Prospect viaduct rehabilitation.  The roadway was closed through June 18 due to clean-up activities and a remediation project began on October 5, 2015.

In 1941, the eastern terminus was moved from US 6 in Port Allegheny to its current location.  In 1952, the route was changed to its current alignment between Marshburg and Ormsby.  Originally, it used the PA 770 and PA 646 alignment.

In 1964, work a new alignment between Kinzua Heights and Marshburg began due to the creation of the Allegheny Reservoir.  A year later, that section opened to traffic. Prior to that, the route went north from near Kinzua Heights to Cornplanter which is now a branch of the reservoir, then in a southeastern direction to Marshburg over what is PA 321.

I-79 to I-376/US 22/US 30

Signed in 1956.  In 1962, the northern terminus was moved from US 22/US 30 in Robinson to PA 51 in Carnot via the Airport Parkway and University Boulevard.

Conceived in the 1963 Pittsburgh transportation plan, this expressway was built to connect the downtown area to the suburban areas to the west and northwest of the city.  Construction began in 1965 from the West Middlesex interchange to the PA 18 interchange.  The following year construction commenced on the Vanport Bridge over the Ohio River and opened the following year.  In 1968, the first section opened to traffic from the West Middlesex interchange to the PA 18 interchange opened to traffic and received the PA 18 designation, as it created a bypass around West Middlesex.  That same year, construction began on the section from Exit 9 to Exit 12.  In 1969, construction began on the section from Exit 13 to Exit 14 while construction was extended from Flaugherty Run Road to Exit 9.

The 1970s began with construction starting in Lawrence County on the section from the current PA Turnpike 60 interchange to Mitchell Road in 1970.  In 1971, the second section of the expressway opened to traffic from Flaugherty Run Road to Exit 12.  That same year, construction was extended from Exit 14 to a half-way point between the exit and PA 51 and the following year it was extended to near PA 51.  In 1972, the section from Exit 13 to Exit 14 opened to traffic and with that the route was moved from ending at PA 978  to ending at Exit 14.

In 1973, the section from the current interchange of PA Turnpike 60 to US 224 opened to traffic, while construction began on the section from that interchange to north of the town of Pulaski.  Construction was extended to PA 51 from Exit 14 in 1974 and in 1975, construction was extended from north of Pulaski to the West Middlesex interchange.  In 1976, the section from Exit 10 to Exit 29 at PA 51 was completely open to traffic and created what would become the end of PA 60 for almost two decades at PA 51.  In that same year, the section from US 224 to Mitchell Road opened as well.  The following year the expressway would from Mitchell Road to PA 18 and signal the completion of the Beaver Valley Expressway minus the section from PA 51 to US 422.  In 1978, the PA 18 designation was moved back to the original route through West Middlesex.

June 14, 1990 marked the beginning of the end for the "missing-link" between PA 51 and US 422.  Built and maintained by the Pennsylvania Turnpike Commission, this section opened from PA 108 to US 422 on November 8, 1991 and the rest of the expressway on November 20, 1992.  That same year, the northern terminus was moved north from I-80 to PA 18, and then seven years later, moved to its final location at Business US 62 in Sharon.

Construction began on the newest part of PA 60, the Southern Expressway, in 1990 to serve the new Midfield Terminal of Pittsburgh International Airport.  This 7.5 mile, $190 million section opened to traffic in September 1992.

On October 17, 2005, US Senator Rick Santorum and US Representative Melissa Hart made an announcement at Pittsburgh International Airport that had been years in coming.  On November 6, 2009, the Interstate 376 designation officially replaced PA 60 from US 22/US 30 to PA 18. 

The route was decommissioned when PA 60 was decommissioned north of the US 22/US 30 cloverleaf and replaced by Interstate 376.

Signed from 1928 to 1936 from Concordville to Chester on Concord Road, Chelsea Road, and Chinchester Avenue in Delaware County.

Signed in 1963 on its current alignment.  In 1983, the route suffered severe subsidence damage in the form of cracks from the Centralia mine fire south of the borough.  The Pennsylvania Department of Environmental Resources paid $500,000 to stabilize the roadway.  In 1987, the Saint Clair bypass was completed and moved traffic out of the borough.

Until 1991, the northern terminus was located at PA 147 in Sunbury.  It was moved to its current location after the new Veterans Memorial Bridge was completed.

In 1992, it was determined that the roadway south of Centralia was beyond repair, and eventually the highway was closed in early 1994.  The PA 61 designation was detoured on the current PA 54 alignment between Ashland and Mount Carmel.  In 1999, the adjacent Byrnesville Road, which carries the SR 2002 designation, was upgraded and now bypasses a section damaged by the underground mine fire that has been burning in Centralia since 1962.

Mine subsidence caused not by fire, but water, caused issues on a section of the roadway in Northumberland in April 2012.  On the afternoon of April 11, a 12-foot-long, 12-foot wide, and five-foot-deep hole opened up in the middle of the road, taking up one and a half lanes and forcing traffic onto the shoulder.  PennDOT crews were on scene all day dumping rocks into the large hole, and then it was covered with concrete and the roadway opened late in the day on April 13.

When body parts are found along highways, it is always a morbid discovery, but that is what crews widening the alignment near Schuylkill Haven in Schuylkill County discovered in August 2015.  On August 13, workers returned to the work zone to discover heavy rains had washed away dirt from an embankment that was being excavated, exposing bone fragments and coffin nails.  The area quickly turned into a crime scene, with cadaver dogs marking other places where remains might possibly be buried.  It was determined that the bodies were not there due to foul play, but the Spanish flu.  "Our working diagnosis is that it was related to the mass epidemic of 1918," said the Schuylkill County coroner, Dr. David Moylan III.  Historical records showed the land had been a cemetery for the old Schuylkill County Poor House.

Experts from Mercyhurst University in Erie collected remains including a leg, ribs, skull fragments and piece of jawbone to be sent back there for analysis.  "Even if we got DNA from these bones, it would be difficult to match them up to people unless we had a cemetery record to compare them or if there were any living relatives that could help us," Dr. Alexandra Klales, post doctoral fellow and adjunct faculty at the university, said.  Experts from Indiana University of Pennsylvania used ground-penetrating radar and discovered mounds that might have been mass graves, along with many individual graves.

PennDOT halted project until it was determined if there were more bodies in the work area.  After consulting with Doctor Moylan, the Federal Highway Administration, and the Pennsylvania Historical and Museum Commission, as well as soliciting public input, it was determined that the widening project would continue without further disturbing the property.  "The human remains … will remain in place and PennDOT will take measures to ensure the [widening project] results in no further impacts to the human remains," the agency said in a statement released on October 6, 2015.

In 1930, the route was paved from Trexlertown to Fogelsville and Claussville to Holbens Valley Road.  SR 0062 is currently assigned to US 62.

In 1934, the section from Beech Creek to Lusk Run Road was under construction and opened the following year.  In 1935, the route was moved to Lusk Run Road.

In 1946, the route was placed on its current alignment between Zion and Mill Hall.  Previous to this, it ran between Milesburg and Mill Hall on what became US 220.

Southern terminus moved from Dale Summit to Zion in 1973.  The northern terminus was moved from Cedar Springs to Mill Hall in 1978.

Signed in its current location in 1961.  The route was widened and a median installed in 1965 between Rochester and Freedom.

Construction would being on the next section of Ohio River Boulevard from near the California Avenue/Marshall Avenue intersection to Pennsylvania Avenue in January 1970.  In 1973, this $16 million section opened to traffic with plans to continue the expressway to the Fort Duquesne Bridge.

With traffic increasing on the North Shore, construction on the $8 million Phase One project to connect the two sections of Ohio River Boulevard together began in Spring 1987 from Allegheny Avenue to Western Avenue.  Phase Two of the project began in January 1988, which consisted of a new interchange between the expressway and the West End Bridge.  The bridge would be closed for two years while it underwent rehabilitation and new ramps were built at the northern end for the interchange.

In 1992, the southern terminus was moved from Western Avenue to I-279 when the missing-link in Ohio River Boulevard was finally closed.

If you were a daily commuter who used Ohio River Boulevard in the later half of the first decade of the 21st Century, you have my sympathy.  Due to construction of a Super Walmart on a hillside where Dixmont State Hospital once stood overlooking PA 65 in Kilbuck Township, landslides started to become a common occurrence.  The first landslide happened on April 27, 2006 after blasting loosened the soil and caused a road closure for two days, but then another happened on September 19 where an estimated 300,000 to 500,000 cubic yards of earth buried the roadway and adjacent Norfolk Southern Railroad tracks.  That last one prompted the Department of Environmental Protection to force Senex Explosives to submit blasting plans before blasting; however, two of the four lanes of the roadway would remain closed for another three years.  Repair work began on June 8, 2009 but had to be halted due to discovery of a damaged footer that supported the median barrier.  Upon PennDOT's review of the plans and approval, work resumed in July with the southbound lanes reopening on August 3, 2009 and the northbound lanes later in that same month.  Due to the unstable nature of the hillside, Walmart withdrew plans for their store in 2007 but assumed responsibility for ongoing maintenance of the site.

In February 2007, the northern terminus was moved from Business US 422 to PA 108/PA 168 at Croton Avenue in New Castle.

A $9.4 million reconstruction project at the Ohio River Boulevard/Marshall Avenue interchange in Pittsburgh began on July 22, 2010.  Phase I included redecking of the ramp from the northbound direction of the expressway and Chateau Street to Marshall Avenue which was completed in November 2010.  Phase II began on July 15, 2011 with the closure of the bridges carrying Ohio River Boulevard over the Marshall Avenue interchange for rehabilitation, and the $20 million phase was completed in November 2011.  Phase III began on January 21, 2013 and included rehabilitating two structures over the Norfolk Southern Railroad line.  The $14.2 million phase was completed in Fall 2013 and marked the end of work.

Another landslide closed PA 65 just north of Interstate 79 in Glenfield on April 6, 2011.  The southbound lanes were reopened that day after it was determined there was no danger to that side.  Heavy equipment was brought in to remove a large boulder that could have fallen onto the roadway, which caused the northbound side to remain closed until April 11.

In 1930, the section from West Virginia to Greensburg was decommissioned in favor for the new US 119 route.  In 1932, the northern terminus was moved from the New York state line to Frysburg.  In 1935, the northern terminus was moved from Fryburg to Tionesta.

Construction on the US 22/PA 66 cloverleaf finished in 1958.  It was replaced with a Single Point Diamond Interchange (SPDI) in 2000 as part of the US 22 rehabilitation.  In 1959, the route was widened from Greensburg to Clopper Street and a median installed from US 22 to north of Delmont and PA 286 to north of PA 366.  

In 1960, the designation was moved from Courthouse Road to bypass Kittanning on its current alignment.  In 1968, route moved onto I-80 to bypass Clarion and onto its current route between Clarion Junction and Kane.  That same year, PA 66 was routed onto its current alignment from US 322 north to its current terminus.  Previous to that year, it followed the PA 208 alignment from US 322 to PA 36 in Frills Corners, then that route north to Tionesta where it ended at US 62.

The only news to come from the route during the 1980s was when the road was widened and a median installed in 1982 from Ford City to US 422.

Construction began on the Amos K. Hutchinson Bypass in August 1990, with the part from US 119 to US 30 opening on July 13, 1993.  The remaining section to US 22 opened on December 9, 1993 and with that, the new expressway assumed the route of PA 66 and the southern terminus moved from Otterman Street in Greensburg to the cloverleaf interchange at US 119 in New Stanton.

Construction began on March 24, 2000 to finish the Kittanning Bypass from US 422 north of Ford City to northeast of Kittanning which opened to traffic on December 13, 2001.

The section of PA 66 north of Delmont in Westmoreland County was a particularly treacherous one for drivers during the winter due to ice; however, it was not coming from the usual source.  Groundwater runoff from a coal mine or coal seam was coming to the surface, and not only damaging the roadway, but causing slick conditions which resulted in numerous accidents.  The problem was corrected by digging a ditch to divert the water away from the road during a resurfacing project in the summer of 2011.

It wasn't an accident, but rather a lovelorn bull and cow that forced the closure of the intersection with PA 85 in Armstrong County on morning of June 1, 2012.  The couple had traveled more than two miles from Alvin Rosenberger's farm.  State Police tried to corral the bovines to the shoulder with crime scene tape, while rubberneckers snapped pictures with their cell phones.  "In this case, we really had to grab the bull by the horns," said Corporal Christopher Robbins.  The lovers were herded into the farmer's trailer for the ride home thanks to portable fencing and a little help from the county emergency management agency and the State Farm Bureau.  "Cows we can deal with – people – that’s a good way to get arrested," added Corporal Robbins.

On May 19, 2003, during a "Click It or Ticket" blitz, a police officer handing out  flyers to drivers on North Main Street near Cabin Hill Drive noticed two men, later determined to be Mexican, sitting up front in the truck were not wearing seat belts. They were told to pull over.  A search of the truck found five other Mexican men lying side by side in the back, concealed by tinted windows. Two women were riding behind the front seats.  None of the occupants spoke English.

In 1956, eastbound traffic was moved to Cunningham Street and McKean Street in Butler.

In 1962, the northern terminus was moved from Kinzua, which is now under the Allegheny Reservoir near Kinzua Heights, to Kane.  In 1968, the northern terminus was moved from Kane to its current location.

At 10 AM on June 4, 2007, the 122-year-old East Brady Bridge that spanned the Allegheny River between Brady's Bend and East Brady, was demolished by explosives.  It had been replaced by a span 300 feet downstream named the Sergeant Carl F. Curran II Bridge which opened on April 26.  It is named in honor of a native of East Brady who was killed near Fallujah, Iraq in 2004 while serving with the Pennsylvania National Guard.

In 1946, the route was moved from Reservoir Street from US 6 to Simpson to Belmont Street.  That year the northern terminus was moved from Susquehanna to the New York state line.

SR 0070 is currently assigned to Interstate 70.

In 1955, the route was moved onto the new expressway from PA 481 to PA 88, from what is currently SR 2016 and Lincoln Avenue from PA 481 to Charleroi.  In 1960, the eastern terminus was moved from the intersection of West Pittsburgh Street and West Newton Street to US 30.

The route was decommissioned on September 10, 1964.

The expressway opened from Zediker Station Road to Bentleyville in 1960.

In 1932, the route was paved from Jonestown to PA 343.  In 1936, the northern terminus was placed at its current location from Lancaster Street at PA 343 north of Jonestown and the southern terminus placed in Goshen.

Until 1946, there was another PA 72 from US 11 to US 309 on Bridge Street, Carey Avenue, River Street, and South Street in Wilkes-Barre.

In 1958, the route was placed on Queen Street for northbound traffic in Lancaster.  Southbound traffic was moved onto 10th Street in Lebanon and a median was installed from Jonestown to Interstate 78 that year.

In 1965, the southern terminus was moved from Goshen to its current location.

In 1970, replaced PA 934 from PA 443 to Lickdale to end at that route.  Six years later, the route's northern terminus was moved to Lickdale.

In 1991, the section that comprises the Cornwall Bypass was upgraded to expressway standards.  In 1995, the current northern terminus was selected.

A year later, PennDOT studied improving the route between PA 283 and the PA Turnpike.  It concluded that left turn lane/shoulder improvements, widening, and “relief routes” around the boroughs of East Petersburg and Manheim would be needed to keep PA 72 from becoming choked with traffic.  However, there is a snag in the funding for this project.  PennDOT released their revised 12-Year Transportation Program in 2004 and this project was deferred.

Signed in 1928 on the current alignment, and the route was paved from the New Hanover Township line to Layfield.  In 1929, the route was under construction  from Schwenkville to PA 113 and completed the following year when the route was paved from PA 23 to Knauers.

In 1931, the route was under construction from Boyertown to Gilbertsville and completed the following year.  In 1954, the route was moved to Perkiomen Avenue for eastbound traffic in Reading.

In 1962, the western terminus was moved from PA 23 in Goodville to Mount Penn.  In 1964, the western terminus was moved from US 422 in Mount Penn to its current location.  In 1968, the route was moved from Frankford Avenue, Robins Avenue (eastbound), and Levick Street (westbound) to its current alignment between US 13 and the Tacony-Palmyra Bridge.

PennDOT began a project to rebuild the route between Washington Lane and Station Avenue in Montgomery County in summer 2004.  Work entailed reconstructing the roadway surface, widening the roadway, improving drainage, add shoulders, and remove a small hill between Willow Grove Avenue and Station Avenue.  The $4.5 million project came to an end in August 2006.

In 1930, the route was paved from Ickelsburg to Marshrun and Donnally Mills to Millerstown.  In 1932, the route was paved from Marshrun to Donnally Mills.  In 1938, the section from PA 944 to Lebo opened, while the same time the sections between Lebo and Bridgeport, and PA 274 to PA 894 were paved.

In 1941, the northern terminus was moved from Carlisle to Ickesburg.  In 1947, the section at the Cumberland and Perry County line was paved.

In 1950, the route between Icklesburg and PA 75 was finished.  Paved from Perry County line to PA 75 in 1953.  In 1951, the route was split from Market Street with Philadelphia Street taking northbound traffic and southbound remaining on Market in York.

Northern terminus was moved from PA 17 in Ickesburg to its current location in 1965.  In 1989, a median was installed on the section at the US 30 interchange in York.

The route was closed August 8, 2009 between the Maryland state line and PA 851 due to delivery of a large transformer to the Peach Bottom Atomic Power Station in Delta.  Another convoy, this time hauling a used 250-ton generator from Three Mile Island, started its trip on May 3, 2010 crawling from PA 24 in Red Lion onto Maryland.

Not one, but two trucks ended up striking the bridge over Interstate 83 in 2022:  one on February 24 and another almost six months later on August 25 which necessitated its closure both times.  The first accident was when a truck hauling an excavator struck the overpass with the boom of the excavator and the second time the bed of a dump truck was raised 45 degrees, hit then became wedged underneath the bridge deck.  Temporary repairs were made in both instances, with the bridge remaining closed until February 28 and the second time reopening August 25 albeit to only one lane in each direction.  PennDOT had been finalizing plans to make repairs, which would have cost $600,000, for the first accident when the second one happened.  Repairs after both will run $1 million to $1.5 million.  The first driver was cited for out of service criteria, exceeding 8-feet, 6-inches in width, exceeding height allowance, and operating with unsafe equipment.  The second driver, who was injured in the accident, received a careless driving citation. 

In 1928, the route was under construction from Fort Loudon to Richmond Furnace and completed the following year.

In 1930, the route was paved from Seven Pines to Turbett.  In 1932, the route was paved from Honey Mills to Seven Pines.  In 1936, the section between Blairs Mill and Waterloo was improved.  In that year the southern terminus was moved from Fort Loudon to the Maryland state line.  In 1938, the section from Berry Ridge Road to East Waterford was paved.

In 1940, the section from the Huntingdon County line to Berry Ridge Road was paved.

In 1930, the section from Cassville to Calvin was paved.  In 1932, the northern terminus was moved from Mill Creek to Reedsville.  Also that year, the highway was paved form Harrisonville to Waterfall, from Saltillo to Knightsville, and from Morgans Road to Mill Creek.  In 1935, the sections from Tonoloway Creek to Harrisonville and Waterfall to Saltillo were paved.  In 1936, the section from South Gordon Lane to Sam's Road was paved.  In 1938, the sections between Colvalt Road and South Gordon Lane and from PA 376 to Cassville were improved.

In 1940, the section between Fisher Road and Needmore was improved while the section between PA 376 and Cassville was paved.  In 1947, the route was paved from Johnsons Mill Road to Colvalt Road.

SR 0076 is currently assigned to Interstate 76.

In 1932, the section from PA 277 to Garland was paved.  In 1934, the section from PA 408 to Little Cooley was under construction and opened the following year.  Also the section from Spring Creek to Eldred Hill Road was paved.

In 1936, the section from Downey Ferry Road to Riceville Road was paved and so was the section from Eldred Hill Road to Chapman Road.  In 1938, the section from Chapman Road to Garland was paved.  In 1941, the section in Garland was paved.

In 1961, the western terminus was moved from Park Avenue to its current location.

In 1977, the eastern terminus was changed from PA 27 in Garland to the current location.  Previous to that, the route traveled to Spring Creek and then followed the current PA 426 alignment to Garland.

In 1930, the route was paved from the Wolf Creek Township line to Sandy Lake and Deckards Run Road to Lake Creek Road.  In 1936, the northern terminus was moved to PA 408 from PA 27. and the southern terminus was moved from Grove City to Slippery Rock.

In 1941, the southern terminus was moved from Slippery Rock to Stone House.  The section from PA 198 to PA 408 was paved in 1946.

SR 0078 is currently assigned to Interstate 78.

Originally, the western terminus was at US 20 in West Springfield and the eastern terminus at US 6 in Elgin.  However, in 1936, the route was truncated to make way for US 6N's new alignment.  And the eastern terminus was cut back from Spartansburg to Concord Corners.

SR 0079 is currently assigned to Interstate 79.

In 1952, the designation was moved off the current PA 380 alignment from PA 286 to Wilkinsburg onto the US 22 alignment and onto the Penn-Lincoln Parkway.  In 1959, the western terminus was moved from the Boulevard of the Allies to the Fort Pitt Bridge.

SR 0080 is currently assigned to Interstate 80.

SR 0081 is currently assigned to Interstate 81.

It was technically not a continuous route from 1987 until 2008.  On September 8, 1987, a tropical depression unleashed a torrent of rain across eastern Pennsylvania, which caused waterways to overflow.  One of those waterways that flooded was Hay Creek south of Birdsboro.  

That night around 9:30 AM, a Geigertown Fire Company engine happened to be crossing one of the spans when the rushing waters to shift it and caused the roadway to collapse.  The engine then became caught in a crevice between the bridge and roadway.  The three firefighters managed to jump from the cab to safety and were not injured.  James Bitler, one of the volunteer firemen, said they had just reached the other side of the bridge when he heard a crack.  Fortunately, three passenger vehicles and a pick-up truck managed to cross safely ahead of the engine.  The following morning, a 34-ton crane from Morris Kreitz & Sons, Inc. of Wyomissing was brought in to remove the fire truck.

Also on scene on September 9 was Department of Transportation engineer Matthew Mazza, who said it would cost millions to replace four bridges and two abutments, and repair the roadway.  Kenneth Fogle, bridge engineer with PennDOT, said that repairs "will not be done overnight."  He said the first order of business was to find an alternate route for people who travel from south of Birdsboro.

The issue still persisted into the 21st Century, where the price tag to repair PA 82 jumped to $40 million.  Another flood in 2005 washed away two large sections of the roadway, which prompted PennDOT to remove two damaged bridges.  Ron Young of PennDOT District 5 said in 2006 he was not certain it would be reopened.  He said, "We are working on a solution as which way to go. Nothing is definite yet."

The decision was finally made on October 31, 2007 when PennDOT announced it had no plans to reopen the long-closed alignment.  Robeson Township supervisors Chairman Roger K. Feeg said he was glad to hear the news although it did not surprise him.  "I'm glad that this is finally decided because it’s been in limbo so long," he said.  Union Supervisor Barbara M. Cole, said her first choice would have been to reopen the road, but as time went on, it became clear it would stay closed.  "The bottom line is, Penn DOT was not going to reopen state Route 82," Cole said.  "It was an exercise in futility."  PennDOT's statement laid out plans to work with local officials and the Federal Highway Administration to turn over control of the closed section to another entity so it could be turned into a recreation area.  "Hallelujah, that's what I say," said Chip Karasin, president of the Hay Creek Watershed Association.  "It is a de facto park, and if it’s more than a de facto park, that will be great."  However, in order for that to happen, Karasin said a pedestrian bridge would need to be built from the end in Birdsboro across the creek as the only way to cross presently is to wade across.  Feeg said he's supported keeping the road closed because it could lead to making the area safer for recreation.  "Nature has sort of taken it back," he said.  "Nature has a way of doing that."

The route was truncated in Elverson in December 2008.  The remainder of the route between there and  Birdsboro became SR 4082 in Chester County, SR 2082 in Berks County, and PA 345 between it and US 422.

In 1932, the route was under construction from Rehersburg to US 22 and paved from US 22 to PA 443.  In 1946, a bypass of Rehrersburg opened to the east of town.  In 1960, the route was moved from New Schaefferstown Road and Four Point Road to a more straight route between the two.

SR 0083 is currently assigned to Interstate 83.

In 1930, the route was paved from Joe's Run Road to the Cummings Township line and Sweetbriar to Wellsboro.  In 1932, the section from the Mifflin Township line to Sweetbriar.  In 1941, the northern terminus was moved to PA 549 from Tioga.

SR 0084 is currently assigned to Interstate 84.

In Spring 1962, ground was broken on a new alignment that would bypass Yatesboro, Rural Valley, Merideth and Nu Mine to the south.  The new alignment opened to traffic in 1964.  The project included reconfiguring the PA 839 intersection to allow the convergence of the old alignment, new alignment as well as PA 839.  Also, the Cowanshannock Creek in Rural Valley had to be rerouted.  After completion, the original route was proposed to become Business PA 85 but that never materialized.

It wasn't an accident, but rather a lovelorn bull and cow that forced the closure of the intersection with PA 28/PA 66 in Armstrong County on morning of June 1, 2012.  The couple had traveled more than two miles from Alvin Rosenberger's farm.  State Police tried to corral the bovines to the shoulder with crime scene tape, while rubberneckers snapped pictures with their cell phones.  "In this case, we really had to grab the bull by the horns," said Corporal Christopher Robbins.  The lovers were herded into the farmer's trailer for the ride home thanks to portable fencing and a little help from the county emergency management agency and the State Farm Bureau.  "Cows we can deal with – people – that’s a good way to get arrested," added Corporal Robbins.

In 1940, the section from the Crawford County line to US 6N was improved.  In 1947, the section from PA 198 to Cambridge Springs was paved.

In 1951, the section from the Crawford County line to US 6N was paved.  In 1953, the section from Cambridge Springs to the Erie County line was paved.

In 1983, the northern terminus was moved from US 19 four miles north of Waterford via Old State Highway 86 Road, Conneauttee Valley Road, and Sharp Road to its current location.

Even though this is signed as PA 86, it does not have the SR 0086 designation because it was moved to Interstate 86 when it was signed in 1999.

The highway was, for lack of a better term, wrecked in the aftermath of flooding caused by Topical Storm Lee in September 2011.  Due to the raging Loyalsock Creek, the roadway was "shredded" in Lycoming County north of PA 973, making travel impossible and forcing PennDOT to close the route on September 8.  An emergency contract was awarded in October 2011 that encompassed repairing the road, debris and deposition removal, excavation, pipe/culvert cleaning, drainage improvements, guiderail upgrades, and new pavement began in the middle of the month on that 1.2-mile-long section and another 0.4-mile-long section north of Montoursville.  The newly rebuilt sections of PA 87 opened to traffic on December 5.

On May 13, 1929, Allegheny County Commissioner Joseph G. Armstrong officiated the ceremony which officially kicked off work on Saw Mill Run Boulevard.  Commissioner E. V. Babcock, Pittsburgh Mayor Charlres H. Kline, Council President James F. Malone, Councilman John S. Herron, and Henry Meuschke, a Castle Shannon resident who advocated for the project as far back as 1910, were in attendance for the ground breaking.  The project was funded by the 1928 "City Beautiful" bond issue, which was to finance other roadways such as Ohio River, Allegheny River, and Mosside boulevards.

In 1930, the route was paved from current PA 201 to current PA 136.    

In 1930, the route was paved from West Brownsville to California.  The designation was moved onto Library Road from Bethel Park to PA 51.  The designation had been signed on Baptist Road to end at PA 51 in Brentwood prior to the construction of Saw Mill Run Boulevard.  Also that year, the first section of Saw Mill Run Boulevard opened from Brownsville Road to the Liberty Tunnel.  The most challenging part of construction was the PA 51 intersection where seven individual roads intersected as well as the convergence of Clairton Run Creek and Saw Mill Run.  In 1935, the northern terminus was moved from PA 51 to Rochester and a year later to New Castle.

Construction on the West End Bypass began in October 1949; however, it had its start a decade earlier.  Robert Moses, New York City planner extraordinaire, had been hired by Pittsburgh to untangle traffic as well as he had done in "The Big Apple."  This was one of his ideas and priced at $900,000 which was approved in February 1941.  The onset of World War II delayed the project, and by the time it was revised, the cost had jumped to $3 million.  It took nearly a year to blast and remove one million cubic yards of material needed to clear its right-of-way on the side of Mount Washington.  Outside of that, another challenge Harrison Construction Company faced was building a ramp from Steuben Street.

In 1952, the West End Bypass opened to traffic from the Penn-Lincoln Parkway to PA 837.  The route was widened and a median installed in 1958 between Freedom and Baden, Ambridge to Edgeworth, and Glenfield to Emsworth.  The same work took place a year later between Baden and Ambridge.

The biggest change to the route took place in 1961 when the northern terminus was moved from New Castle to its current location.

In 1975, construction began on the section of expressway from Low Hill Road to US 40.  This section opened in 1977.

In 1983, the designation was moved onto the expressway section from Low Hill Road to US 40, and then multiplexed with US 40 to the exit with its original route.  In 1984, when the newest section of the Mon-Fayette Expressway opened between Exit 32 and Exit 34, the designation was moved onto it from its route hugging the cliff along the Monongahela River.  It was moved back to the original route in 1991.

If you drive though the intersection at PA 51 and Maytide Street can be a nasty bottleneck.  However, PennDOT is exploring making changes at that intersection.  The varying plans call for building an interchange all the way to keeping the at-grade intersection but improving it with jughandles to eliminate left turns.

After nearly 80 years of service, the Point Marion Bridge, or Albert Gallatin Memorial Bridge, that carried PA 88 over the Monongahela River, was deemed unsafe and construction on a replacement began on January 7, 2008.  The new $21 million crossing opened on October 22, 2009, and the original was imploded on November 16, 2009.

A sinkhole caused by mine subsidence led to closure of the route in Allenport on August 6, 2009.  The hole was estimated at 12 feet wide and 20 feet deep and repairs took three weeks to complete.

On May 13, 2011, the route was closed to traffic near Fredericktown due to a rock slide.  It was not just dirt and trees that fell, but large boulders that were far too large to be removed by PennDOT equipment alone.  It took until June 2 for PA 88 for the debris to be removed.

Those who drive PA 88 knew all too well that the intersection at PA 51 and Maytide Street in Pittsburgh could be a nasty bottleneck.  Ideas for improving the intersection first came to light in March 1992 and right-of-way acquisition began in 1998.  However, PennDOT District 11 determined that the high cost of the project combined with the minimal congestion that it would alleviate did not warrant funding, prompting five alternatives to be studied between 2002 and 2004.  Costs for the alternatives ranged from $45 to $84 million, and again, the project was put on hold due to lack of funds.  The design was modified again and presented at a public meeting on October 4, 2010, with final design, utility coordination, and right-of-way acquisition begun shortly after.  The $19 million project began in August 2013 and included replacement of five bridges, construction of a new bridge, upgrading signals, lighting, and sidewalks, installation of traffic cameras, as well as improving drainage and stream bank restoration.  Two jughandles were built to aid PA 51 traffic, one of which for northbound vehicles wanting to turn left onto PA 88 and Glenbury Street.

In 1932, the section from Concord Corners to Ovid was paved.  In 1936, the section from Beaverdam to Ladd Road was paved.  That year the southern terminus was moved from Elgin to Titusville.

The route was paved from Concord Corners to Darrows Corners in 1938 and so was the section from Ladd Road to Wattsburg. In 1940, The section from the Rome Township line to East Brach of Oil Creek was paved.

In 1941, the section from the East Brach of Oil Creek to PA 77 was paved.  In 1953, the northern terminus was moved to its current location from US 20 in North East.

In 1932, the route was paved from Stroudsburg to Analomink, Cresco to Haags Mills and Dyberry to Equinunk.  In 1934, the section from just north of Stockport to the New York state line was under construction and opened the following year.  In 1938, the section from Monroe County line to Ledgedale Road was paved, while the section from there to Hamlin was improved.  Also the section from just north of Stockport to town was paved.

In 1940, the section from Ledgedale Road to Hamlin was paved and Hoadleys to Terrace Street in Honesdale was improved.  In 1941, the southern terminus was moved from US 611 in Stroudsburg to US 22 in Easton via the current PA 191 alignment to Stockertown and Sullivan Trail to Easton.  Also the section from Equinunk to Stockport was paved.  In 1946, the section from Hoadleys to Terrace Street in Honesdale was paved

PA 90 was planned to be revived for the Pulaski Expressway in Philadelphia, but it's construction was cancelled.  SR 0090 is currently assigned to Interstate 90.

In 1932, the route was paved from the Luzerne County line to Tunkhannock and from Lenox to Gelatt.  In 1934, the sections from Nicholson to Lenox and Gelatt to Susquehanna were under construction and opened the following year.

In 1940, the section from the Luzerne County line to Bowman Creek was paved.  In 1946, it swapped alignments with PA 309 between West Pittston and Bowman Creek.  Prior to that the route started in Kingston at US 11.

A bridge replacement project in Luzerne County became flooded on July 8, 2019 during a torrential rain storm.  The project site in Exeter, to replace the bridge spanning Hicks Creek, was inundated with water which submerged a mini excavator and Bobcat.

In 1946, the eastern terminus was moved from Buffalo Creek Road at PA 45 east of Mifflinburg to Lewisburg.

SR 0095 is currently assigned to Interstate 95.

In 1936, the section form Willis Creek to Shirey Road was paved.  In 1938, the section from Hyndman to Willis Creek was paved.  In 1973, the northern terminus was moved from Pleasantville to its current location.

In 1928, the route was under construction from Town Hall Road Kearsarge and completed the following year.  In 1930, the section from Sharp Road to Town Hall Road was paved.  In 1935, the section from Waterford to Sharp Road was paved.

Signed on its current alignment in 1936.

Until 1955, the southern terminus was in Meadville.  That year it was moved to its current location.

In 1936, it was signed on its current alignment.  In 1952, construction started on a new alignment north of Middleboro and finished in 1953.  In 1962, the northern terminus was moved from US 20 in Erie to its current location, eliminating the multiplex into Erie from Millcreek.  In 1971, the route was widened and a median installed from near Interstate 79 to US 19.

This was the last state route in Pennsylvania to share an SR designation with another route.  The SR 0099 designation is now solely used to designate Interstate 99 when its final section opened between Bald Eagle and State College in 2008.

In 1956, the Pottstown bypass opened from south of the city to old US 422.  In 1958, the route was widened and a median installed from Pottstown Pike in West Chester to Exton.  In 1958, the designation was moved back to the old route, and the following year the segment from West High Street to north of the city opened.

In 1964, a median was installed from Pottstown to New Berlinsville, and moved back out of Pottstown.

In 1970, what would become a future part of the route opened to traffic.  That section being the expressway segment from US 202 to Pottstown Pike in West Chester.  In 1971, the route was widened and a median installed from Exton to Lionville.  The following year the same was performed from south of Pottstown to West High Street.

In 1989, the route was widened and a median installed from Lionville to the Pennsylvania Turnpike interchange.

Construction began on Phase One of the Trexlertown Bypass on April 26, 2002 which involved earth moving and placement of more than one million cubic yards of earthen fill at the interchange area near Breinigsville and a replacement wetland area near Trexlertown Road and Spring Creek Road.  The advance contract was necessary to allow the embankments time to settle and compress the clay layers beneath the interchange.  This phase was completed in late 2002 at a cost of $6.8 million.

On April 4, 2003 construction began on Phase Two of the bypass which begins south of Spring Creek Road and ends north of Ruppsville Road.  The new $46.5 million highway opened on September 27, 2005 and the designation removed from Trexlertown Road.

In 2003, the southern terminus was moved from the Delaware state line one-half mile south of Cossart to US 202.  The move came at the request of West Chester residents who complained about the amount of traffic going through the borough.

On June 16, 2005, PennDOT announced work would begin on a $13.6 million project to install ITS equipment on PA 100 in Chester County.  Over the next 15 months, crews installed 33 closed circuit TV cameras, 22 dynamic, and 61 incident detectors along the route as well as US 30 in Chester County and US 202 in Delaware and Chester Counties.  They are connected to the Philadelphia Traffic Management Center in King of Prussia.

A widening and improvement project began June 1, 2014 on 2.5 miles of Pottstown Pike in Chester County.  Aside from expanding the route from two to three lanes in each direction to create a six-lane roadway from US 30 to the Pennsylvania Turnpike, five jug handles will be replaced with turning lanes at certain intersections, installing new traffic signals, replacing the metal median divider with a concrete barrier, modifying the storm water collection system, and adding storm water management facilities.  Sound wall, retaining wall, and sidewalk installation will also be part of the project, as well as constructing a truck weigh station on the northbound side at the current Ship Road jug handle.  The project finished in February 2016.