U.S. Highway 191 (US 191) is a north-south United States Numbered Highway in the state of Montana. It extends approximately 442.2 miles (711.7 km) from Yellowstone National Park north to the Canadian border.

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U.S. Highway 191
US 191 highlighted in red
Route information
Maintained by MDT
Length	442.161 mi[1] (711.589 km)
Major junctions
South end	Yellowstone National Park at West Yellowstone
Major intersections	US 20 / US 287 in West Yellowstone I-90 from Bozeman to Big Timber US 89 in Livingston US 12 in Harlowton US 87 from Moore to Lewistown US 2 in Malta
North end	Hwy 4 at the Canadian border at Morgan
Location
Country	United States
State	Montana
Counties	Gallatin, Park (Wyoming), Park (Montana), Sweet Grass, Wheatland, Fergus, Phillips
Highway system
United States Numbered Highway System List Special Divided Montana Highway System Interstate US State Secondary
← MT 141 → MT 200

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US 191 in Montana begins at the West Entrance to Yellowstone National Park concurrent with US 20 and US 287, at the edge of the town of West Yellowstone. Some commercially produced maps show US 191 going through Yellowstone National Park; however, it officially has a gap inside the park and resumes in Wyoming at the South Entrance. A few blocks into West Yellowstone, US 20 leaves the US 191 / US 287 concurrency and heads west toward the Targhee Pass and Idaho. The highway heads north, running concurrently with US 287 for eight miles (13 km) before veering slightly east and passing through Yellowstone National Park for 20 miles (32 km), traversing forested, mountainous terrain and briefly following a 5.5-mile (8.9 km) diversion into the state of Wyoming, before leaving the park in the upper reaches of the Gallatin River canyon. The route travels northward through the narrow canyon, past the resort community of Big Sky, then entering the Gallatin Valley near the town of Gallatin Gateway. US 191 travels north and east through the valley to the city of Bozeman, which is the largest city along the entire US 191 route.^[1][2]

From Bozeman, US 191 is concurrent with I-90 eastward 60.5 miles (97.4 km) to Big Timber, where it proceeds north. The road travels through hilly ranch country near the eastern edge of the Crazy Mountains to Harlowton, where US 191 is briefly concurrent with US 12. North of Harlowton, US 191 is concurrent with MT 3 for 39 miles (63 km) to Eddie's Corner, where US 191 proceeds eastward to Lewistown on a roadway shared with US 87 and MT 200, in a wrong-way concurrency.^[1][2]

US 191 continues north after going through Lewistown, crossing the Missouri River at the Charles M. Russell National Wildlife Refuge, and through Malta, where it shares a brief concurrency with US 2. It ends at the Canada–United States border at Morgan, where the road continues into Saskatchewan as Highway 4 toward Swift Current.^[1][2]

The routing of US 191 has drastically changed through the years, with original route designated in 1926 ran from Idaho Falls, Idaho, to West Yellowstone concurrent with US 20, which existed until 1981 when US 191 rerouted to its current alignment through Wyoming, Utah, and Arizona.^[3]

On February 1, 1935, US 191 was extended over Montana Highway 187 (also known as the Gallatin Way) to Bozeman.^[4]

In 1996, US 191 was extended from Malta the Canadian border, absorbing former Montana Secondary Highway 242.^[3]

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