Signed on its current alignment in 1936.

In 1954, the eastern terminus was moved to Baltimore Pike via Cobbs Creek Parkway.  The route used Chestnut Street and Sixth Street for eastbound traffic and Fifth Street and Walnut Street for westbound.  The terminus was US 30 at the foot of the Ben Franklin Bridge in Franklin Park.  A median was installed in 1958 between Newtown Square and Upper Darby.

In 1962, the highway was widened and a median installed on it between West Chester and Newtown Square.  Also, the route was moved from ending at US 13 at 52nd Street via Cobbs Creek Parkway and Baltimore Avenue to 43rd Street.

In 1974, the route's eastern terminus was moved from 43rd Street to its current location.

In 1928, not only was the route's eastern terminus moved to Philadelphia via the US 22, PA 653, US 322, PA 34, PA 274, US 322, and PA 3 alignments but it was under construction from Covallen to Cove and completed in 1929.  In 1929, the route was under construction from Dunncannon to Covallen and Downingtown to Alton.  Those two sections were completed the following year.

In 1932, the route was moved onto the current PA 99 alignment from Erie to Cambridge Springs.  In 1936, the route was removed from traversing Pennsylvania from northwest to the southeast and signed in Erie County in 1936 on its current alignment except in Erie where it followed the current Alternate PA 5 alignment.  Also that year, the section from US 20 to the Fairview Township line was paved.

In 1955, the route swapped alignments with Alternate PA 5 in Erie.  Work to widen and install a median from Barnes Road to Orchard Beach Road in Northeast took place in 1958.

Median installation continued in the City of Erie in 1966 from Raspberry Street to Peach Street and Ash Street to Payne Avenue.  The last segment to be reconfigured was in 1982 at the Interstate 79 interchange, where the route was widened and a median installed from the City of Erie line to Greengarden Road as part of the interchange construction.

In 1931, the route was under construction between Mayport and the Jefferson County line and was completed the following year.  In 1934, the section between the Allegheny County line and Three Degree Road was under construction, and opened in 1935.

In 1958, construction began on the section from Grant Avenue to PA 28 in Etna.  This section opened in 1959.  The year 1958 also saw the route widened and a median installed on its from Franklin to Reno.  In 1961, the section from the end of the Richard C. Frame Memorial Highway to Franklin was upgraded with a median, and in 1968 the section from Reno to Oil City received the same.

In 1973, construction began on the section of expressway from Pearl to the northern of the expressway south of Franklin in Venango County.  That same year, its southern terminus was moved from West Carson Street in Pittsburgh to PA 28 in Etna.  In 1974, construction began from the southern end at Wesley to PA 308 and finished in 1976.  In 1977, the southern terminus was moved to its current location from PA 28 in Etna.  In 1979, the route was moved to bypass Oil City and replaced Bypass PA 8.

Signed in 1956.  In 1963, the northern terminus was moved from PA 23 in Morgantown to its current location.

Revived in 1928 to mark a route from Center Valley to Bartonsville following the PA 378, PA 512, and parrelling the current PA 33 expressway from Stockertown to Bartonsville.  This was decommissioned in 1961.

Construction on the expressway that would become PA 12 began from US 222/US 422 to Business US 222 in 1964 and finished in 1965.  In 1977, construction began on the remaining section from Business US 222 to Spring Valley Road and finished the following year.  The expressway would not receive the designation until 1999.

SR 0013 is currently assigned to US 13.

Signed in 1928 on the current alignment.  In Williamsport, it followed Washington Boulevard, Market Street and Hepburn Street for northbound traffic, while southbound used Pine Street and Sixth Street.  In 1929, the route was under construction from PA 325 to Herdon and Trout Run to Marsh Hill and both completed the following year.

In 1930, the route was paved from Millersburg to the Northumberland County line, Dalmatia to PA 325, Boile Run Road, and Dewart to Montgomery.  In 1931, the route was under construction from Fisher Ferry to Sunbury and from Ralston to Penbryn and was finished the following year.  In 1932, the route was paved from Millersburg to Dalmatia.  In 1936, the southern terminus was moved from Millersburg to Harrisburg when the route was moved from the eastern shore to the western shore to multiplex with US 11 on that side.  

In 1941, it was moved from the western shore of the Susquehanna from Wormleysburg to Northumberland to the eastern shore.  From Milton it followed the current PA 405 alignment to Muncy.

In 1955, the southern terminus was moved from Oakleigh at Paxton Street to Clarks Ferry.  In Harrisburg it followed South 40th Street, Derry Street, Mulberry Street, and Front Street.

In 1963, the southern terminus was moved from US 22/US 322 in Clarks Ferry to its current location.  Prior to the move it came in via Washington Boulevard and High Street.

From 1928 to 1930, it was on the current PA 317 alignment from the Ohio state line to Mt. Jackson.  From 1930 to 1933, it was signed on the current US 224 alignment.  In 1930, the section from the Ohio state line to Peanut was paved.

The current alignment received the PA 17 designation in 1928, but only from Millerstown to Liverpool.  In 1936, the western terminus was moved from Millerstown to its current location.

From 1987 to 1999, there were two PA 17s, with the other one designating the current I-86 to continue the NY 17 designation.

In 1928, the route was moved to its current alignment between PA 158 and Greenville.  Originally, it traveled the current PA 158 and PA 58 alignments.  That year it was under construction from US 30 to Service Church Road and Hill Road to PA 198 and completed the following year.  In 1929, the route was under construction from Harshaville to Service, which was finished the following year.  Also that year, paving was done from Nettle Hill to Whitecottage, Gretna to current PA 50 and Shaffer Road to Shippingport.

In 1932, the section from West Virginia to Nettle Hill, Florence to US 30, and Green Garden Road to Mowry Road was paved.  In 1935, the section from Nineveh to the Washington County line was paved.  A year later, the section from the Greene County line to Old Concord was paved.

In 1958, the route was widened and a median installed between PA 551 and Koppel.

In 1963, the designation was moved from Liberty Street, Atlantic Avenue, and Washington Street in New Castle to its current alignment on Mahoning Avenue and Jefferson Street.  In 1967, the route was widened and a median installed from PA 60 to Monaca.

In 1970, the route was widened and a median installed from PA 518 to Clark.  Also that year, work to widen and install a median on the route from Clark to Transfer began. Construction was extended from Transfer to Shenango in 1971 and in 1972, work on those sections were completed.  In 1971, the route was widened and a median installed from US 62 to Highland Road.

The designation was moved to the PA 60 expressway from its current alignment between the West Middlesex interchange and the end of the Beaver Valley Expressway in 1970.  Moved back in 1978 and eliminating the Business PA 18 designation through West Middlesex.

In October 2001, work began to widen the highway to five-lanes in Hermitage City.  This project finished in November 2002.

For years, Geneva College in Beaver Falls has lobbied PennDOT to rectify a dangerous S-curve near the campus.  Aside from safety, the route cut into part of the campus which prevented expansion.  In Fall 2006, PennDOT began work to realign PA 18 which was completed in November 2007.

In 1932, the route was paved from Coal Lick Road to Baileys Crossroads, Crucible Road to Jacobs Ferry, and from East Riverside to Hibbs.

In 1946, the route was changed to follow the current alignment between Paisley and Uniontown.  Prior to that, it went northeast from Carmichaels via Arensburg Road, Penncraft Road, Millsboro Road, New Salem Road, Herbert Road, and Dearth Road and then multiplexed with US 40 to end at PA 51 at Pittsburgh Street in Uniontown.

In 1953, the route was shifted from Georges Road between Baileys Crossroads and Carmichaels to its current route between Baileys Crossroads and Paisley.  Also that year, a new alignment was under construction from west of Masontown to east of McCellandtown which opened in 1954.  The highway was widened and a median installed from east of Paisley, Masontown and Leckone, and in McClellandtown in 1958.

Morrisville to Curry Home Road was opened in 1966 moving the designation off Rolling Meadows Road and Curry Home Road.  A median was installed from east of Paisley to the Monongahela River in 1967.

With PennDOT restructuring their 12-Year Transportation Program, the project to improve PA 21 in Greene and Fayette Counties will be reevaluated.

In 1957, the route was moved from North Spring Road and Conshohocken State Road to Gulph Road, Springs Mill Road, Old Gulph Road, Morris Avenue, and Mill Creek Road between Valley Forge and Philadelphia.

In 1965, the western terminus was moved from Lancaster to its current location.  In 1967, it was moved from Gulph Road, Springs Mill Road, Old Gulph Road, Morris Avenue, Mill Creek Road to its current route between Valley Forge and Philadelphia.

Construction began in 1976 on the "goat path expressway."  In 1978, the expressway project was cancelled by locals not wanting all the excessive traffic.  The "goat path expressway," as it is referred to was covered by dirt.  However, there has been talk of reviving this project to accommodate growing traffic levels.  PennDOT has been studying how to improve PA 23 from US 30 to PA 772, which is where the original expressway would have been built.  However, now that the restructured 12-Year Transportation Program has been released, this is now being reevaluated.

In 1984, the eastern terminus was moved from the intersection of US 30/Girard Avenue and Belmont Avenue to the current location.  Construction began on the alignment from Walnut Street in Lancaster to US 30 and opened in 1993.  This caused the route to be moved off New Holland Pike from Walnut Street to US 30 and onto this new alignment.

In 1951, the route was split from Market Street with Philadelphia Street taking northbound traffic with southbound remaining on Market in York.  In 1961, the northern terminus was moved from I-83 at Exit 39A to its current location.  In 1973, the northern terminus was moved from US 30 in Yorkshire to its current location.  The following year, the route was widened and a median installed from US 30 to Eastern Boulevard in Yorkshire.

In 1938, the section from Miller Road to Clearville was improved.

In 1940, the sections from the Fulton County line to Inglesmith and from Chapmans Run to Clearville were paved.  In 1946, the section from Millers Corners to Champmans Run was improved.

In 1955, the section from Inglesmith and Millers Corners was improved.

In 1963, the northern terminus was moved from Huntingdon to Bellefonte.  also the section from Millers Corners to Chapmans Run was paved.  In 1967, the northern terminus was moved from Huntingdon to Howard and two years later it was moved again, this time to its current location.

Construction began on the Bellefonte Bypass in 1971 and opened in 1972 as a "Super-2" expressway, a two-lane expressway built on a four-lane right-of-way.  The other two lanes would not be added until 1997.

In 1973, the route was changed from following the current PA 150 alignment to its current route north of State College to Bellefonte and Howard Street and Jacksonville Road to PA 26.  In 1974, the route through State College changed.  The northbound direction was moved to South Buckhout Street, Beaver Avenue, and High Street with the southbound direction remaining on College Avenue.

In 1989, the section between Inglesmith and Millers Corners was paved, thus completing PA 26.

In 1974, the western terminus was moved from Park Avenue to US 6/US 19 via Spring Street, Terrace Street, and North Street.  The western terminus would move back to Park Avenue in April 2003.

In 1958, the highway was widened and a median installed at the interchange with the Turnpike.  In 1961, the highways southern terminus was moved from Independence to PA 8 in Etna.

In 1963, this section opened to traffic from PA 8 north to the Highland Park Bridge interchange and the following year to Blawnox.  

Also that year, the Pittsburgh Area Transportation Plan recommended upgrading PA 28 and then PA 8, to a six-lane, limited-access highway starting 2,200 feet west of the 31st Street Bridge and ending at the 40th Street Bridge.  Full interchanges would be constructed at both bridges; however, this recommendation was not carried out.  It also laid out a plan that would turn PA 28 into an expressway from Pittsburgh to Brookville, this too was not carried out.

In 1964, the highway was widened and a median installed on it between Brackenridge and the Butler County line.  In 1968, construction began on the section from Blawnox to PA 910.  The expressway was proposed from that point to the Butler County line.  Construction also began on the section from Slate Lick to near Center Hill in the same year.  In 1965, the route was moved from Courthouse Road into Kittanning to bypass the borough on its current alignment.  In 1969, construction commenced on the section from PA 910 to Exit 12 and from Exit 16 to PA 356 and the Armstrong County line.

The start of the 1970s saw the construction extend from Exit 16 all the way to a new expressway alignment for US 422, also under construction, near West Kittanning.  In 1971, construction commenced on the section from Exit 15 to Exit 16.  In 1972, the expressway opened to traffic from Blawnox to PA 910 and from Exit 15 to US 422.  However, PA 28's designation was not placed on the section from Exit 15 to Exit 16.  The following year, the expressway opened from PA 910 to Exit 12.

In 1973, the route was extended to end at US 19/PA 65 at Chateau Street via Western Avenue and East Ohio Street.  In 1975, construction commenced on the section from Exit 12 to north of Tarentum; and during the following year, the construction was extended to Exit 15.  In 1978, the PA 28 designation was routed onto the newly opened highway from Exit 11 to Exit 12 and from Exit 15 to Exit 16.  The PA 28 designation still followed Freeport Road to connect between Exit 12 and Exit 15.

In 1980, the expressway opened from Exit 12 to Exit 13 and the PA 28 designation was moved onto this section.  In 1984, the route was changed to follow Western Avenue, Allegheny Avenue, North Shore Drive, General Robinson Street, and Madison Avenue for northbound traffic, and Reedsdale Street for southbound traffic in Pittsburgh.  The final section of the Allegheny Valley Expressway between Exit 13 and Exit 15 opened in 1985.

Construction began in 1985 on a new alignment from Ninth Street to East Ohio Street near the H. J. Heinz plant as part of the I-279/I-579 completion project.  The new alignment opened but PA 28 wasn't removed from North Side streets onto the current route until 1993.  That year the southern terminus was moved from the West End Bridge to its current location.

Construction began on March 24, 2000 to finish the Kittanning Bypass from PA 66 to PA 85, and was opened to traffic on December 13, 2001.

The interchange with I-279 at the southern end of the route was always a thorn in the side of drivers since it opened in 1989.  For southbound drivers wanting to continue onto I-279 south, they had to exit onto East Ohio Street and travel through three traffic signals just like a certain "town of motels" in Bedford County.  Construction on a ramp to provide a direct connection began on March 31, 2008 which weaves over Madison Avenue and under the Veterans Memorial Bridge ramps, and connects to the existing I-279 on-ramp from East Ohio Street that drivers have always used.  The new $7.9 million ramp opened to traffic on September 25, 2008.

In 1970, the southern terminus was moved from West Chester via Phoenixville Road and Phoenixville Pike to its current location.  In 1989, the route was widened and a median was installed at the Interstate 78 interchange in Allentown.  The same occurred from US 202 to US 30 in 1991.

In 1934, the section from US 6 to Franklin Forks was under construction and opened the following year.  In 1936, the sections from Evans Falls to Rosengrants and Franklin Forks to the New York state line were paved.  It was also rejoined to complete the route between Hazleton and Tunkhannock.  In 1938, the section between Rosengrant to Tunkhannock was paved.

In 1940, the section between Bowmans Creek and Evans Falls was paved.  In 1946, PA 29 was routed onto its current position between West Nanticoke to Silkworth.  Also, removed from Cragle Hill Road and Swamp Road onto US 11 from Shickshinny to West Nanticoke.

Construction on the expressway from north of Sugar Notch to the Nanticoke interchange began in 1969.  Work extended to I-81 in 1971 and it opened to traffic in 1972.  In 1978, the designation was finally signed onto this section and the southern terminus moved to I-81 from West Nanticoke.

In 1932, the route from Dividing Ridge to Manns Choice was paved.  In 1934, the section from Clay Pike Road to Donegal was under construction and opened in 1935.

In 1954, the route was widened between Laurelville and County Line Road.  Two years later the route was widened between Mount Pleasant and Mellingertown.

In 1964, the western terminus was moved from the West Virginia state line to its current location.

Then from 1928 to 1932, the route was signed from Carlisle to Mecks Corner and then the northern terminus was moved to Juniata Bridge in 1936.  The route follwed the current PA 34, PA 274, and US 11/US 15 alignment.  From 1936 to 1941, it ran between Shippensburg and Carlisle on the current US 11 alignment.  That year it flipped alignments with US 11.

From 1936 to 1963, PA 33 was designated to what is currently PA 174 between Shippensburg and Mooredale and PA 465 to Allen Road to Carlisle.  In 1938, the section between Foltz Road and McCalisters Road was paved.

Construction on the current PA 33 alignment began in 1959 from the PA 512 interchange to the Saylorsburg interchange.  Construction finished in 1960, and with the the PA 90/PA 115 designations were moved onto the new highway.  The next section to see construction was from Saylorsburg to Interstate 80 in 1963 and finished in 1964.

A construction drought occurred from 1964 to 1969, when in that year work began on the section from US 22 to PA 512.  A year later, the section from the Belfast interchange to the PA 512 interchange opened to traffic.  The section from PA 191 to the Belfast interchange opened in 1971 and from US 22 to PA 191 finished in 1972.  With the expressway complete, PennDOT gave PA 33 its fourth home in 45 years.

One section missing was from US 22 to the rerouted Interstate 78, that now bypassed the Allentown-Bethlehem-Easton area to the south.  That problem was rectified in March 1999 when work began on the trumpet interchange at I-78.  $104.6 million project.  The main line of the three-plus mile Route 33 Extension and its new interchanges with Freemansburg Avenue and I-78 opened on January 20, 2002.

Sinkholes have always been a problem near the Stockertown area.  That problem came to light on January 24, 2004 when one developed under a support pier on a bridge carrying PA 33 north over Bushkill Creek.  The expressway was closed between PA 248 and PA 191 until temporary crossovers could be built to detour traffic.  Measures were taken to try and salvage the bridge, but in the end the ground won out as more developed in the area.  The end result was the demolition of the structure which began on February 2, 2004.  If one sinkhole was bad enough, another was discovered a mere 21 days later between the southbound bridge and where the former northbound bridge stood.  PennDOT's geotechnical engineering staff determined that it posed no problems to PA 33, and the void simply filled with fill material.  Crews noticed vertical movement in the southbound bridge on February 27, but deemed it not to be a threat.  However, on April 21, a depression formed near the northbound crossover that was built to detour traffic around the damaged bridge.  The expressway was closed for 20 minutes between 10 AM and 11 AM so crews could fill the depression with bituminous material.

Eventually the southbound bridge also had to be demolished which began on July 8.  The new northbound bridge opened on June 24, 2004 and its southbound counterpart on November 19, 2004. 

In 1963, the southern terminus was moved from Gettysburg to the Maryland state line after US 15 was moved onto the Gettysburg Bypass.  However, it didn't stay on that alignment for long, as in the same year it was moved back to its current location.  In 1967, the northern terminus was moved to from Newport to the US 22/US 322 expressway and then finally in 1970, it was moved to US 11/US 15.

In 1930, the route was paved from Walnut to Mifflin.  In 1932, the route was paved from Shade Gap to the Juniata County line.  In 1935, the section from Reeds Gap to just south of McKinley Road was paved.  In 1938, the section from Peru Mills to Noss Road was paved.

In 1940, the section from just north of the Huntingdon County line to Peru Mills was paved.  In 1941, the section in between the county line and that point was paved.

In 1930, the section from Miller Street to the Clearfield County line and Creek Road to Ostend.  That year, the southern terminus was moved from Washington Avenue and 12th Avenue in Altoona, to replace the US 220 designation from Pleasant Valley Boulevard to Washington Avenue on Union Avenue and Ninth Avenue.  In 1931, the route was under construction between the Indiana County line and Punxsutawney, and was finished the year later along with paving from McGees Mills to the Jefferson County line.  In 1932, the route was paved between Nagle Road and Pine Run Road, Oliveburg and Brookville, Sigel and Leaper, Tylersburg and Frills Corners.  Also that year, the route was moved from 12th Avenue and 16th Street to 18th Avenue and 22nd Avenue.  In 1936, the northern terminus was moved from Frills Corners to its current location and replaced PA 860 between Tylesburg to Frills Corners.  Also the southern terminus was moved from Altoona to its current location at the Maryland state line.  In 1938, the section from Newmansville to Brush Road was paved.

In 1946, the route was changed between Tylesburg and Frills Corners via Lickingville to its current route, displacing PA 860.

In 1962, route changed to current alignment from Saint Boniface to the Clearfield County line.  Prior to that, the route when thru Hastings.  In 1965, the route was moved from North Juniata Street and Plank Road to Logan Boulevard between Hollidaysburg and Altoona.  In 1971, the northbound traffic was moved to Union Avenue in Altoona.

In 1946, the designation was moved from the current PA 590 alignment from Greeley to Lackawaxen to the current PA 434 alignment between Greeley and the New York state line.

Signed in 1936.  In 1972, work began to widen and install a median from Lucknow to Terrace Drive, and concluded in 1973.  In 1989, the route was widened and a median installed from West Chocolate Avenue to US 322/US 422 interchange in Hershey.

Signed in its current location in 1928.  In 1930, the route was paved from Gap to Belmont Road and Cherry Hill Road to Fairview Road.  In 1932, the northern terminus was moved from US 222 in Lampeter to its current location.

PennDOT has been planning improvements to the route in Chester County near Avondale.  However, with the revised 12-Year Transportation Program unveiled, this project is being reevaluated.

In 1928, the route was under construction From Catawissa to Bloomsburg and Mordansville to Millville, and both sections were finished in 1929.  In 1929, the route was under construction from Numidia to Catawissa and from Rupert to Bloomsburg.  Both sections were completed the following year.

In 1930, the route was paved from Aristes to the Locust Township line and from Bloomsburg to Fairview Drive.  In 1932, the route was paved from current PA 239 to Beech Glen.  In 1938, the section between PA 442 and the Lycoming County line was improved.

In 1940, the section between PA 442 and the Lycoming County line was paved.  In 1941, the section between the Columbia County line and PA 118 was paved, and the section between there and PA 239 was paved in 1946.

From 1928 until 1946, there was another section in Chester County from PA 272 in Chrome to US 1 in Barnsley on Barnsley-Chrome Road.  In 1935, the route was truncated form Reading to Barnsley.

In 1949, the section from Eagles Mere to Laporte was paved.  In 1969, the route was widened and a median installed from Rupert to Interstate 80.

Resigned in 1952 on the Schuylkill Expressway, but only lasted until 1964 when it was removed.

Resigned in 1993 for only four miles of the Mon-Fayette Expressway, due to the fact it was built by PennDOT.  Construction began in 1991 and concluded in 1993.

In 1930, the route was paved from US 220 to Ramseyville and Millport to Sharon Center.  In 1932, the route was paved from Oleona to Carter Camp and from near Patterson State Park to south of Sweden Valley.  Also from Ramseyville to current PA 414 was paved.  Construction began on a section near Patterson State Park was in 1934 and opened the following year.  In 1935, the section from current PA 414 to just north of Pump Station was paved as was the section from PA 49 to Ridge Road.  In 1936, the southern terminus was moved from Jersey Shore to Turbotville.  In 1936, the section near the Patterson State Park was improved and from Hebron Center to Whitney Creek Road was paved.  In 1938, the section from Ridge Road to Hebron Center was paved.

In 1941, the southern terminus was moved to Mahanoy City form Jersey Shore.

In 1953, the section from Pump Station to Olena was improved.  In 1954, Cherry Springs to Carter Camp was improved.  In 1955, a segment from Carter Camp north was improved.  In 1959, a segment north of Cherry Springs was paved. 

In 1964, the southern terminus was moved from Mahanoy City to its current location.  In 1967, the section from the Clinton County line to the Potter County line was paved.  In 1969, the route was widened and a median installed from Rupert to Interstate 80.

In 1970, the route was moved onto the US 220 expressway to Jersey Shore.  In 1977, the section from the Clinton County line to Oleona and north and south of Cherry Springs was paved.

In 1989, the section from the southern side of the Susquehannock State Forest to Carter Camp was paved which marked the completion of the route.

In 1930, the route was paved from Lehigh Gap to Indianland on the eastern section.  In 1934, the eastern terminus was moved from Walnut Street to 13th Street in Easton.  In 1936, the eastern terminus was moved from Montandon to Mausdale in the middle section.

Until 1952, the route entered Mooresburg.  In 1951, construction began on a bypass which opened in 1952.  In 1955, the eastern terminus in the eastern section was moved from 13th Street to Third Street in Easton.

From 1932 to 1961, there was another PA 45 from Belsano to US 22 west of Ebensburg.  The route replaced US 422 from Belsano to US 22 and US 22 from Ebensburg to Cresson.  In 1946, it was truncated from Sankertown to Ebensburg.  Until 1961, there was a break between Mausdale and Ashland, that was connected when PA 54 was truncated to Mausdale.

In 1962, the route was changed from going into State College via US 322 and then PA 26, to go straight from PA 26 to Boalsburg and in 1966 the eastern section was terminated leaving the current alignment the only one to hold the designation.

In 1931, the route was under construction from North Creek Road to near the McKean County line.  that section was paved the following year, as was from that last point to the PA 146 intersection.  In 1932, the route was paved from Bradford to the New York state line.

From 1932 to 1946, there was another section from Sandy Ridge to Osceola Mills in Centre County.

In 1968, the northern terminus was moved from the New York state line via Interstate Parkway to its current location.

In 1946, the route was changed to its current alignment between Lincoln Way and US 30.  The route ran along Lincoln Way, State Street, and Foster Road to end at US 30 in East McKeesport.

In 1954, the northern terminus was moved from US 30 to its current location.

Even though the expressway idea was axed, PA 48 received much need upgrades.  The two-lane highway was widened and resurfaced and new guide rails were installed in a section from US 30 to Ross Street in Wall in 1988.  The $2.4 million project began on July 28, 1988 and ended in October 1988.

In 1998, the northern terminus was moved from I-376 at Exit 14 to Business US 22.

In 1929, the route was under construction from Lent Hollow Road to Gold, and completed the following year.  Also that year, the section from Lewisville to Mills was paved.  Also in 1929, the route was under construction from Marsh Road to Lawrenceville and completed in 1930.

In 2003, the western terminus was moved from Coudersport to its current location.

Signed in 1961.  In 1974, work to widen and install a median on the route between Cecil and Bridgeville began and concluded three years later.