U.S. Route 20 in Montana

U.S. Highway 20
US 20 highlighted in red
Route information
Maintained by MDT
Length	9.680 mi[1] (15.578 km)
Existed	June 3, 1940–present
Major junctions
West end	US 20 at the Idaho state line
Major intersections	US 191 / US 287 in West Yellowstone
East end	West Entrance of Yellowstone National Park
Location
Country	United States
State	Montana
Counties	Gallatin
Highway system
United States Numbered Highway System List Special Divided Montana Highway System Interstate US State Secondary
← MT 19 → MT 21

U.S. Route 20 (US 20) is a transcontinental east–west U.S. Highway that travels between Newport, Oregon, and Boston, Massachusetts. It passes through southern Montana for approximately 10 miles (16 km), connecting Targhee Pass at the Idaho state line to the town of West Yellowstone and the West Entrance of Yellowstone National Park near the Wyoming border.

A series of early roads across Targhee Pass were constructed in the late 19th century and were replaced by plans for a modern highway following the establishment of West Yellowstone. The new highway was completed by 1928 as part of US 191 and was incorporated into an extension of US 20 in 1940. US 191 was removed from the highway in 1978.