State Highway 51
SH-51 highlighted in red
Route information
Maintained by ITD
Length	93.598 mi[1] (150.631 km)
Major junctions
South end	SR 225 near Owyhee, NV
Major intersections	SH-78 SH-67 near Mountain Home
North end	I-84 BL in Mountain Home
Location
Country	United States
State	Idaho
Counties	Owyhee, Elmore
Highway system
Idaho State Highway System Interstate US State
← SH-50 → SH-52

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.^[2]

As currently configured in the state's official milepoint log, SH-51 terminates at the Business Loop 84 intersection with American Legion Boulevard, and is not otherwise officially concurrent/overlaid with BL-84 (where the signs at I-84's Exits 90 and 95 say "To SH-51/To SH-67") or the former section of US-20 that follows American Legion Boulevard to Interstate 84/U.S. Route 20 east at Exit 95. As of February 2015, some map products such as Google Maps still show SH-51's former overlay with American Legion Boulevard.^[1]

Route description

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 11.5 miles (18.5 km) 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 4 miles (6.4 km) south of the state border. After another 95 miles (153 km) through Elko County, SR 225 connects with Interstate 80 in Elko.

History

The basic route of today's SH-51 was in place as early as the 1930s, mostly as an all-weather gravel road from Mountain Home until it reached the northern boundary of the Duck Valley Indian Reservation, and as an unimproved road on through to the Nevada border and then-NV Route 11 as of the 1937 map.^[3]

Major intersections

County	Location	mi[1]	km	Destinations	Notes
Owyhee	Duck Valley Indian Reservation	0.000	0.000	SR 225 south to I-80 – Owyhee, Elko, Reno	Southern terminus of SH-51
		1.458	2.346	BIA Road 7
		2.925	4.707	BIA Road 8
		7.260	11.684	BIA Road 211
	​	69.715– 69.916	112.195– 112.519	SH-78 west – Grand View, Marsing	Western end of SH-78 overlap
	​	76.582	123.247	SH-78 east – Bruneau Dunes State Park, Hammett	Eastern end of SH-78 overlap
Snake River		76.979	123.886	Snake River bridge; Owyhee–Elmore county Line
Elmore	Mountain Home	88.294	142.095	West 36th Street South	Old Grandview Road
		90.785	146.104	SH-67 west – Mountain Home AFB, Grand View
		91.948– 93.598	147.976– 150.631	I-84 BL – Boise, Glenns Ferry, Twin Falls	Overlap on I-84 Bus. (old US-26/30) to official northern terminus at American Legion Blvd. (old US-20)
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus

Elevation

Elevation on the highway ranges from a low of 2461 feet (750 m) above sea level at the Snake River crossing,
to a high of 5400 feet (1646 m) at the Nevada border.