Route information | ||||
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Maintained by PennDOT | ||||
Length | 59.409 mi[1] (95.610 km) | |||
Existed | 1932–present | |||
Major junctions | ||||
South end | ![]() | |||
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North end | ![]() | |||
Location | ||||
Country | United States | |||
State | Pennsylvania | |||
Counties | Chester, Montgomery, Berks, Lehigh | |||
Highway system | ||||
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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.