Imperial (named from the Imperial Valley, which in turn was named from the Imperial Land Company, the developer of the region) is one of the 58 counties in the state of California. It was created in 1907 from the eastern half of San Diego county. It was the 58th, and last, county to be created in California (to date). As of the 2010 census, the population was 174,528, up from 142,361 in 2000. The county seat and largest city is El Centro.
Imperial measures 4,481.7 square miles (11,608 km2) in area, of which 4,176.6 square miles (10,817 km2) is land. It is bordered by San Diego County on the west, Riverside County to the north. La Paz County, Arizona to the northeast and Yuma County, Arizona to the southeast. To the south it borders Municipio de Mexicali and Municipio de Tecate, both in Baja California.