High Quality Content by WIKIPEDIA articles! U.S. Highway 431 (US-431), internally designated by the Alabama Department of Transportation as State Route 1 (SR-1), is a major north–south state highway across the eastern part of the U.S. state of Alabama. Although US-431`s south end is in Dothan, SR-1 continues south for about 13 miles (21 km) along US-231 to the Florida state line.