High Quality Content by WIKIPEDIA articles! U.S. Route 1 (US 1) is the easternmost and longest of the major north–south routes of the United States Numbered Highway System, running from Key West, Florida to Fort Kent, Maine. In the U.S. state of Maryland, it is an 80.86-mile (130.13 km) segment of the route that runs through central Maryland between Mount Rainier and Rising Sun.