Sevier County, Utah  Sevier County ( ) is a county in Utah, United States. As of the 2010 United States Census, the population was 20,802. Its county seat and largest city is Richfield. Evidence of indigenous peoples residing in the Sevier County up to 5,000 BP has been unearthed. The Fremont culture of Native Americans occupied the area from about 2000 to 700 BP. The Clear Creek site contains native petroglyphs from that period. In Utah, the Numic- (or Shoshonean) speaking peoples of the Uto-Aztecan language family evolved into four distinct groups in the historic period: the Northern Shoshone, Goshute or Western Shoshone, Southern Paiute, and Ute peoples. The central and eastern sections of this territory were occupied primarily by various bands of the Ute. The first European-based persons to see the Sevier River were most likely Catholic fathers Silvestre Vélez de Escalante and Francisco Atanasio Domínguez, on their expedition to California in 1776. The Old Spanish Trail was the route they mapped. Over the next century this trail carried fur trappers, hunters, government officials, and settlers. Permanent colonization of this area began when Richfield was first settled. Mormon settlers arrived on June 15, 1864, most of whom had emigrated from Scandinavian countries. Because of the growth in this small community, the people soon petitioned Utah Territory officials about a separate county. On January 16, 1865 the Utah Territory legislature created the county, with area annexed from Sanpete County. It was named for the Sevier River. The county seat was Big Spring (later named Richfield). The county borders were adjusted in 1866, in 1880, in 1890, and in 1921. A clarification of boundary lines corresponding to government survey lines was completed in 1931, marking the present configuration of Sevier County. Although the county was in place by 1865, much of Sevier County was abandoned in the Black Hawk War in 1867. Attempts to resettle the area were not successful until 1870. By 1874, 753 residents lived in the area. Sevier County terrain consists of semi-arid but arable rolling areas, punctuated by northeast-southwest oriented mountain ridges, usually forested. The highest point is Fish Lake Hightop in the Central Utah Plateau, at 11,633' (3546m) ASL. The county has a total area of , of which is land and (0.4%) is water.