Riverside is the county seat of Riverside County, California, United States and is also a focus city of the Greater Los Angeles Area. The city is named for the nearby Santa Ana River. As of 2006, Riverside had an estimated population of 305,255. In 2005, Riverside was the largest city in the Inland Empire region, the 61st-largest city in the United States, and by one measure part of the 14th-largest metropolitan area in the nation.. Riverside apartments for rent comparison page shows most up to date rent information on Riverside apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.