High Quality Content by WIKIPEDIA articles! Riverside is a city in Riverside County, California, United States, and the county seat of the eponymous county. Named for its location beside the Santa Ana River, it is the largest city in the Riverside-San Bernardino-Ontario metropolitan area of Southern California, 4th largest inland California city after Fresno, Sacramento, and Bakersfield, and is located approximately 60 miles (97 km) east of Los Angeles. Riverside is the 61st most populous city in the United States and 12th most populous city in California. As of the 2010 Census, Riverside had a population of 303,871. The city spans 81 square miles (210 km2).