Previously part of the Mexican Territory of Alta California, the Clark County lands were subsequently traversed by American beaver trappers. Paiutes moved into the area as early as AD 700. Native Americans lived in the Las Vegas Valley beginning over 10,000 years ago. The Las Vegas Valley, a 600 sq mi (1,600 km 2) basin, includes Las Vegas and other major cities and communities such as North Las Vegas, Henderson, and the unincorporated community of Paradise. The county was formed by the Nevada Legislature by splitting off a portion of Lincoln County on February 5, 1909, and was organized on July 1, 1909. Las Vegas, the state's most populous city, has been the county seat since its establishment. It covers 7% of the state's land area but holds 73% of the state's population, making Nevada the most centralized state in the United States. It is by far the most populous county in Nevada, and the 11th most populous county in the United States. Most of the county population resides in the Las Vegas Census County Divisions, which hold 2,196,623 people as of the 2020 Census, across 435 square miles (1,130 km 2). As of the 2020 census, the population was 2,265,461. Clark County is a county located in the U.S.