Idaho State Highway 51 February 2015, some map products such as Google Maps still show SH-51's former overlay with American Legion Blvd. SH-51's northern terminus is in the city of Mountain Home in Elmore County. After turning south from Airbase Rd. and the intersection with SH-67, the road crosses the Snake River into Owyhee County and passes through the towns of Bruneau, Grasmere, and Riddle. About from the state border it enters the Duck Valley Indian Reservation. As the road crosses into Nevada it becomes State Route 225. The reservation's only major town, Owyhee is about south of the state border. After another through
Alabama State Route 51 reaches its northern terminus at Opelika. When SR 51 was formed in 1940, it covered only the route between Clayton and Midway. The highway was extended to its current southern terminus in 1957, and was extended to its current northern terminus in 1986. Alabama State Route 51 State Route 51 (SR 51) is a state highway in the southeastern and east-central parts of the U.S. state of Alabama. The southern terminus of the highway is at an intersection with U.S. Route 84 (US 84) near New Brockton. The northern terminus of the highway is at an interchange with I-85/US 29/US