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
Maryland Route 51 state highway reduces to a two-lane road after passing Uhl Highway, an old alignment of MD 51 that is unsigned MD 51E. The rail yard ends at Mexico Farms Road, which provides access to Mexico Farms Airport and the Warrior Run Generating Station. Within the hamlet of North Branch, MD 51 intersects as other end of Uhl Highway as well as Pittsburgh Plate Glass Road, which serves the North Branch Industrial Complex, including Federal Correctional Institution, Cumberland. MD 51 enters a rural area and parallels the C&O Canal southeast through Spring Gap. The state highway turns away from the Potomac