Highway 51 (AR 51, Ark. 51, and Hwy. 51) is a designation for two north–south state highways in Southwest Arkansas. One route of 53.37 miles (85.89 km) begins Highway 53 near Whelen Springs and runs north to US Highway 67 (US 67) in Donaldson. A second route of 7.92 miles (12.75 km) runs parallel to US 270 northwest of Malvern. Both routes are maintained by the Arkansas Department of Transportation (ArDOT). A four-mile-long (6.4 km) historic section of Highway 51 remains in Clark County, and is listed on the National Register of Historic Places.