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
Black Tern Bog State Natural Area in southwest Vilas County, approximately northwest of Arbor Vitae. Access is via an unnamed dirt road off US Highway 51, north of the bog. The road wraps around the northern and eastern portions of the bog. It is also possible to park on the shoulder of US Highway 51, which passes along the western edge of the bog. Black Tern Bog State Natural Area Black Tern Bog State Natural Area is a Wisconsin Department of Natural Resources-designated State Natural Area featuring 20 acres (8 ha) of quaking sphagnum bog surrounding two small seepage lakes situated in a pitted outwash plain.