South Dakota Highway 40

Highway 40
SD 40 highlighted in red
Route information
Maintained by SDDOT
Length	37.369 mi[1] (60.140 km)
Existed	1976–present
Major junctions
West end	US 16A in Keystone
Major intersections	SD 79 in Hermosa
East end	BIA 41 in Red Shirt
Location
Country	United States
State	South Dakota
Counties	Pennington, Custer, Oglala Lakota
Highway system
South Dakota State Trunk Highway System Interstate US State
← SD 38 → SD 42

South Dakota Highway 40 (SD 40) is a state highway in southwestern part of the US state of South Dakota. The highway is just over 37 miles (60 km) long and runs from U.S. Route 16A (US 16A) in Keystone to Bureau of Indian Affairs Highway 41 (BIA 41) in Red Shirt. The highway runs near Mount Rushmore National Memorial in Keystone, and its eastern terminus is on the Pine Ridge Indian Reservation near the edge of Badlands National Park.