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.

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 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 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.

In 1952, 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.

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.

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

If you drive PA 51, you know the intersection at PA 88 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.  Whatever is chosen as the final building option, the work will not begin until 2008 at the earliest.

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.

In 1970, the southern terminus is moved from the Maryland state line to US 219.  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.

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 Mt. 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 moved the designation 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.

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.

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 and Marshburg began.  A year later, that section opened to traffic. Prior to that, the route went north from Kinzua to Cornplanter then in a southeastern direction to Marshburg over what is PA 321.

I-79 to PA 18

Signed in 1956.  In 1962, the northern terminus was moved from US 22/US 30 to PA 51 in Carnot.

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.

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 has been years in coming.  By January 1, 2009, the Interstate 376 designation will appear along the PA 60 corridor from US 22/US 30 to PA 18.  At that time, the PA 60 designation will be truncated to an undetermined point in Allegheny County and more than likely at the US 22/US 30 cloverleaf.  It is not know what will become of the section from PA 18 into Sharon.

Improvements to the associated expressways such as the cloverleaf at US 22/US 30 and the designation change were included in the "Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users" highway reauthorization bill passed two months earlier.  Cost for the extension is estimated at $80 million to bring the expressways to Interstate Standards, but doesn't have to be completed for 25 years and certainly not by the target date of New Year's Day 2009.

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 St. 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.

In 1930, the route was paved from Trexlertown to Fogelsville and Claussville to Holbens Valley Road.

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.  A median was 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 would begin in January 1988, which would consist 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.

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

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 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, the northern terminus was moved from Tionesta to its current location.  A median was 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.  With that, the southern terminus was moved from Otterman Street in Greensburg to its current location.

Construction began on March 24, 2000 to finish the Kittanning Bypass.  This section opened to traffic on December 13, 2001.

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.