Pennsylvania Route 100 runs from West Chester in Chester County to Pleasant Corners outside of Allentown in Lehigh County, in the process passing through Exton, Pottstown, Boyertown and some of Allentown's western suburbs. It has freeway interchanges with U.S. Route 30, the Pennsylvania Turnpike, U.S. Route 422 and Interstate 78, and overlaps with U.S. Route 222 through Trexlertown-Breinigsville.