Pennsylvania Route 100

Pennsylvania Route 100
Route information
Maintained by PennDOT
Length	59.409 mi[1] (95.610 km)
Existed	1932–present
Major junctions
South end	US 202 near West Chester
Major intersections	US 30 in Exton PA 113 in Lionville I-76 Toll / Penna Turnpike near Lionville PA 401 in Ludwigs Corner PA 23 in Bucktown US 422 near Pottstown PA 73 in Gilbertsville PA 29 from Hereford to Shimerville US 222 in Trexlertown I-78 / US 22 in Fogelsville
North end	PA 309 in Pleasant Corners
Location
Country	United States
State	Pennsylvania
Counties	Chester, Montgomery, Berks, Lehigh
Highway system
Pennsylvania State Route System Interstate US State Scenic Legislative
← PA 99 → PA 101
← US 62 PA 62 → PA 63

Pennsylvania Route 100 (PA 100) is a 59.4-mile (95.6 km) long state highway in the U.S. state of Pennsylvania that runs from U.S. Route 202 (US 202) near West Chester north to PA 309 in Pleasant Corners. The route runs between the western suburbs of Philadelphia and the Lehigh Valley region of the state, serving Chester, Montgomery, Berks, and Lehigh counties. PA 100 intersects several important highways, including US 30 in Exton, the Pennsylvania Turnpike (I-76) near Lionville, US 422 near Pottstown, US 222 in Trexlertown, and I-78/US 22 in Fogelsville. Several sections of PA 100 are multi-lane divided highway with some interchanges, including between US 202 and the Pennsylvania Turnpike in Chester County between south of Pottstown and New Berlinville, and between Trexlertown and Fogelsville.

PA 100 was originally designated as PA 62 in 1927, running between the Delaware border south of Chadds Ford and US 309/PA 312 in Allentown. PA 62 was rerouted to reach its northern end at PA 29 (now PA 309) in Pleasant Corners a year later. A northern section of PA 62 was designated between PA 15 in Wilkes-Barre and US 106/PA 7 (now US 6) in Tunkhannock in 1927, being replaced with PA 92 a year later. In 1932, PA 62 was renumbered to PA 100 to avoid duplication with US 62. In the 1950s, the route was realigned between south of Bechtelsville and Bally. PA 100 was moved to its four-lane alignment between south of Pottstown and New Berlinville in the 1960s.

Between the 1950s and 1960s, the northern terminus was cut back to Fogelsville with US 309 replacing the route north of there. The section of the route between Exton and Lionville was widened between the 1950s and the 1970s. A freeway along the route in Chester County was proposed in the 1960s, with a short section built between PA 100 south of Exton and US 202 north of West Chester. The southern terminus of PA 100 was moved from Delaware Route 100 (DE 100) at the state line, and placed at the south end of the freeway connector to US 202, in 2003 in order to reduce through traffic in West Chester. PA 100 was rerouted to bypass Trexlertown in 2005. A bypass of Eagle called Graphite Mine Road was completed in 2009, but PA 100 remained on its original alignment after the bypass was built.