Idaho State Highway 51 Idaho State Highway 51 State Highway 51 (SH-51) is a state highway in southwestern Idaho from Mountain Home south to the Nevada border, where it continues as State Route 225 to Elko. It is the major north–south road in Owyhee County. As currently configured in the state's official milepoint log, SH-51 terminates at the BL-84 intersection with American Legion Blvd., and is not otherwise officially concurrent/overlaid with BL-84 (where the signs at I-84's Exits 90 and 99 say "To SH-51/To SH-67") or the former section of US-20 that follows American Legion Blvd. to I-84/US-20 east at Exit 95. As of
U.S. Route 51 in Louisiana intersects LA 38, the main east–west thoroughfare, at Avenue G. The highway curves to the northeast on the way out of town and continues for another to the state line. During this stretch is the final junction with a state route, LA 1054, in an area known as Greenlaw. Immediately across the state line, US 51 continues into the Pike County, Mississippi town of Osyka en route to McComb. The portions of US 51 not concurrent with I-55 are generally classified as an urban or rural major collector by the Louisiana Department of Transportation and Development (La DOTD). However, the