U.S. Route 191

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U.S. Route 191
US 191 highlighted in red
Route information
Auxiliary route of US 91
Length	1,544.54 mi[1][2][3][4] (2,485.70 km)
Existed	1926–present
Major junctions
South end	SR 80 in Douglas, AZ
Major intersections	I-10 in Willcox, AZ I-40 in Sanders, AZ US 491 in Monticello, UT I-70 / US 6 / US 50 by Green River, UT US 6 in Price, UT US 40 in Duchesne and Vernal, UT I-80 / US 30 in Rock Springs, WY US 14 / US 16 / US 20 in Yellowstone Nat'l. Park I-90 in Bozeman, MT US 2 in Malta, MT
North end	Hwy 4 at Canada–US border near Loring, MT
Location
Country	United States
States	Arizona, Utah, Wyoming, Montana
Highway system
United States Numbered Highway System List Special Divided
National Forest Scenic Byway

U.S. Route 191 (US 191) is a north–south highway in the Western United States and a spur of parent route U.S. Route 91 that has two segments. The southern segment runs for 1,102 miles (1,773 km) from Douglas, Arizona on the Mexican border to the southern part of Yellowstone National Park.^[1][2][3] The northern segment runs for 442 miles (711 km) from the northern part of Yellowstone National Park to Loring, Montana, at the Canada–US border.^[4] Unnumbered roads within Yellowstone National Park connect the two segments. The highway passes through the states of Arizona, Utah, Wyoming, and Montana.

The highway was designated in 1926 and its routing has changed drastically through the years. The modern US 191 bears almost no resemblance to the original route, which was primarily in the state of Idaho. Most of the current route of US 191 was formed in 1981. Since the extensions in the 1980s and 1990s, U.S. Route 191 is much longer than its parent route to which it no longer connects, and it is one of the longest U.S. three-digit routes.