Stockton is a city in and the county seat of San Joaquin County, California, United States. It is the most populous city in the county, the 11th-most populous city in California and the 60th-most populous city in the U.S, with 320,804 residents at the 2020 census. The city is located on the San Joaquin River in the northern San Joaquin Valley, within California's Central Valley. It lies at the southeastern corner of a large inland river delta that isolates it from other nearby cities, such as Sacramento and the San Francisco Bay Area.