U.S. Route 1 (US 1) is a major north–south U.S. Route, extending from Key West, Florida, in the south to Fort Kent, Maine, at the Canada–United States border in the north. In the U.S. state of Pennsylvania, US 1 runs for 81 miles (130 km) from the Maryland state line near Nottingham northeast to the New Jersey state line at the Delaware River in Morrisville, through the southeastern portion of the state. The route runs southwest to northeast and serves as a major arterial road through the city of Philadelphia and for many of the suburbs in the Delaware Valley metropolitan area. South of Philadelphia, the road mostly follows the alignment of the Baltimore Pike. Within Philadelphia, it mostly follows Roosevelt Boulevard. North of Philadelphia, US 1 parallels the route of the Lincoln Highway. Several portions of US 1 in Pennsylvania are freeways, including from near the Maryland state line to Kennett Square, the bypass of Media, the concurrency with Interstate 76 and the Roosevelt Expressway in Philadelphia, and between Bensalem Township and the New Jersey state line.

Morrisville is a borough in Bucks County, Pennsylvania, United States. It is located just below the falls of the Delaware River opposite Trenton, New Jersey. The population was 9,809 in the 2020 Census.