High Quality Content by WIKIPEDIA articles! El Centro is a city in and county seat of Imperial County, the largest city in the Imperial Valley and the east anchor of the Southern California Border Region, and the core urban area and principal city of the El Centro metropolitan area which encompasses all of Imperial County. El Centro is also the largest American city to lie entirely below sea level (- 50 feet). The city, located in the far southeastern corner of California, is conveniently near the major Southern California cities of San Diego and Los Angeles to its west as well as Phoenix and Tucson to its east.