St. George is a city in and the county seat of Washington County, Utah, United States. Located in southwestern Utah on the Arizona border, it is the principal city of the St. George Metropolitan Statistical Area (MSA). The city lies in the northeasternmost part of the Mojave Desert, adjacent to the Pine Valley Mountains and near the convergence of three distinct geologic areas and ecoregions: the Mojave Desert, Colorado Plateau, and the Great Basin. The city is 118 miles (190 km) northeast of Las Vegas, Nevada, and 300 miles (480 km) south-southwest of Salt Lake City, Utah, on Interstate 15.