U.S. Route 191 is a spur of U.S. Route 91 that has two branches. The southern branch runs for 1,465 miles (2,358 km) from Douglas, Arizona on the Mexican border to the southern part of Yellowstone National Park. The northern branch runs for 440 miles (708 km) from the northern part of Yellowstone National Park to Loring, Montana, at the Canadian border. Roads within Yellowstone National Park connect the two branches. The highway passes through the states of Arizona, Utah, Wyoming, and Montana.
The routing of US 191 has drastically changed through the years having been extended and shortened several times. The original route designated in 1926 ran from Idaho Falls, Idaho, to West Yellowstone, Montana along the route now numbered U.S. Route 20. West Yellowstone is the only town that has been continuously served by the highway since its commissioning. As US 191 has mostly been extended while US 91 has largely been truncated, US 191 is now ten times longer than its parent.
At one time US 191 connected to its parent, US 91, twice: at Idaho Falls, Idaho and Brigham City, Utah. Today the highway does not connect to its parent, or even enter Idaho. In Utah, there have been 2 completely different iterations of U.S. 191 serving different areas of the state. The original iteration is now State Route 13, which is mostly a frontage road for Interstate 15.
See also: U.S. Route 191 in Utah#History
By 1981, due to the construction of Interstate 15 and extension of other U.S. Highway designations, US 191 had been truncated to a route between West Yellowstone and Malta, Montana. Utah andWyoming lobbied AASHTO to create a single highway that would connect several National Parks in their states to facilitate tourism. The initial proposal was to extend U.S. Route 163 north into Wyoming. However it was later decided to add Arizona to this proposal for a new highway and instead extend US 191 south. Most of the southern extension recycled existing U.S. and state highways. However, some new sections were constructed. When the 1981 extension was finished, US 191 reached Interstate 40 in Arizona.
In Wyoming, the new US 191 absorbed what was U.S. Route 187, formed in 1926 as a branch from US 87W (now US 287) at Jackson Lake Junction, Wyoming south to US 30 in Rock Springs. Although it became part of US 191 in 1981, the American Association of State Highway and Transportation Officials still lists it in their latest log (1989), with a short independent section in Rock Springs between former US 30 (now US 30 Business) and I-80.
A combination of new construction and the upgrading of county roads created a more direct route between Interstate 80 in Wyoming and Flaming Gorge Reservoir.
Through Utah, US-191 absorbed SR-33, SR-260, and most of SR-44. From Crescent Junction to Bluff was previously numbered U.S. Route 163, eliminating all but a short segment of that route.
A new route was constructed for US 191 from Bluff, Utah to a junction with U.S. Route 160 in Arizona. The 1981 extension caused US 191 to enter Arizona for the first time in its history. Between US 160 and I-40 the highway absorbed the route of former State Route 63.
In 1992, Arizona requested a new number for its portion of U.S. Route 666, arguing the road signs on this highway were the most frequently stolen in the state. As a result, US 191 was extended again to the Mexican border at Douglas, Arizona. In 1996 it became the latest U.S. highway to run from border to border, with the extension from Malta, Montana to the Canadian border, absorbing former Montana Secondary Highway 242. In 2003 New Mexico asked AASHTO to renumber its portion of US 666. This time all of then US 666 was renumbered U.S. Route 491, the x91 number was decided because the road meets US 191 in Monticello, Utah.
US 191 begins at the Mexico border in Douglas. US 191 has a 10-mile (16 km) layover with US 70 east of Safford. The route links to AZ 366 and AZ 266 to the south of Safford. US 191 intersects Interstate 10 in Cochise County. The route between Springerville and Morenci was designated a National Scenic Byway and given the name of Coronado Trail Scenic Byway, as this approximates the path taken by Francisco Vásquez de Coronado between 1540 and 1542. This is a very dangerous mountain road with many sharp curves and little or no shoulders on steep cliffs. The highway is the primary route to access Canyon de Chelly National Monument. US 191 traverses the Navajo Nation before entering Utah.
In 2010 the route was extended from the original terminus at its intersection with Arizona State Route 80 near Douglas Arizona and, with a layover on Route 80, extended to Pan American Ave in the city, then along Pan American Ave to the US Customs/Immigration Port of Entry at the border with Mexico. The portion of this route between its intersection with Arizona Route 80 near Douglas AZ and the intersection with Interstate 40 at Sanders Arizona was formerly the major Arizona portion of US 666.
Main article: U.S. Route 191 in Utah
US 191 serves the eastern half of the state. The road enters Utah in a remote portion of the Navajo Nation. The highway passes through mostly desolate areas of eastern Utah. Several portions are National or Utah Scenic Byways. It passes through Moab, the largest city in southeastern Utah and the seat of Grand County. In addition to linking many rural towns in Utah to Interstate 70 and U.S. Route 40, the highway served to interconnect several national and state parks for tourism. The highway exits Utah just after crossing the Flaming Gorge Reservoir.
US 191 enters Wyoming near a geographical feature known as Minnie’s Gap, just east of Flaming Gorge National Recreation Area. The route proceeds north through rugged desert country following an alignment mostly constructed during the 1970s, to a junction with Interstate 80 at Exit 99, just west of Rock Springs. This segment of the route is known locally as “East Flaming Gorge Road.”
The route is then concurrent with Interstate 80 eastward for approximately 5 miles (8.0 km), passing just north of Rock Springs. US 191 diverges northward at Exit 104, following the former route of US 187. Traveling through high desert country, the route passes through Eden, Farson, and Pinedale before meeting US 189 at Daniel Junction. Continuing north, the road traverses increasingly mountainous terrain, entering the Bridger-Teton National Forest and passing through the small community of Bondurant before descending through the narrow Hoback River Canyon to an intersection with US 26 and US 89 at Hoback Junction. The route than follows the Snake River valley northward to Jackson. US 191 is concurrent with US 189 between Daniel Junction and Jackson, and with US 26 and US 89 between Hoback Junction and Jackson.
North of Jackson, US 191 soon enters Grand Teton National Park, running concurrently with US 26 and US 89. The highway meets US 287 at Moran Junction, inside the park; US 191, US 89, and US 287 are concurrent north of Moran, but the highways are not signed. Continuing through forested, mountainous country, the route passes through the John D. Rockefeller, Jr. Memorial Parkway, and then enters Yellowstone National Park at the park’s South Entrance. No official routing of US 191 through Yellowstone has been designated.
US 191 in Montana begins at the West Entrance to Yellowstone National Park, at the edge of the town of West Yellowstone. The highway heads north, running concurrently with US 287 for eight miles (13 km) before veering slightly east and re-entering Yellowstone. US 191 continues northward through Yellowstone, traversing forested, mountainous terrain and briefly looping 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, before entering the Gallatin Valley near the town of Gallatin Gateway, Montana. US 191 travels north and east through the valley to the city of Bozeman. Bozeman, with a 2010 census population of 37,280, is the largest city on the entire US 191 route.
From Bozeman, US 191 is concurrent with Interstate 90 eastward 58 miles (93 km) to Big Timber, where it proceeds north. The road travels through hilly ranch country near the eastern edge of theCrazy Mountains to Harlowton, where US 191 is briefly concurrent with US 12. North of Harlowton, US 191 is concurrent with Montana Highway 3 for 37 miles (60 km), to Eddie’s Corner. US 191 proceeds eastward from Eddie’s Corner to Lewistown, on a roadway shared with US 87 and Montana 200, in a wrong-way concurrency.
US 191 reaches the Canadian Border after going through Lewistown, across the Missouri River at the Charles M. Russell National Wildlife Refuge, and through Malta. Its northern terminus at the international border is called Port Morgan, and the road continues into Canada as Saskatchewan Highway 4, toward Swift Current, Saskatchewan.