very dangerous mountain road with many sharp curves and little or no shoulders on steep cliffs. North of the byway, the highway is the primary route to access Canyon de Chelly National Monument. US 191 traverses the Navajo Nation before entering Utah. US 191 has a detached business route in Arizona, running from SR 80/Historic US 80 in Douglas, 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 SR 80 near Douglas and the intersection with Interstate 40 at Sanders was formerly the major Arizona portion of US 666. Part of US 191 through the Navajo Nation is designated by the Arizona Department of Transportation as the Tse'nikani Flat Mesa Rock Scenic Road. 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 Bluff, Blanding, Monticello (the seat of San Juan County), and Moab, the largest city in southeastern Utah and the seat of Grand County. It connects with U.S. Route 6 and 50 (temp)as it joins Interstate 70 going due west through the town and crossing the major river at Green river, home to the John Wesley Powell Museum. A few miles out of town it splits off I-70 and continues north between the San Rafael Reef to the west and Book cliffs to the east through Emery County. It then enters the historic coalfields of Carbon County, passing through Wellington, Price, largest city in Eastern Utah home to the USU Eastern Prehistoric museum, and historic Helper, the main stop for Amtrak between Provo Ut and Grand Jct. Colorado.In addition to linking many rural towns in Utah to I-70 and US 40, the highway served to interconnect several national and state parks for tourism, namely Canyonlands National Park, Arches National Park, Bears Ears National Monument, and Dead Horse Point State Park. The highway exits Utah just after crossing the Flaming Gorge Reservoir. Wyoming 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