Antioch, city, Contra Costa County, western California, on the San Joaquin River, near the mouth of the Sacramento River; incorporated 1872. It is a rapidly growing residential, industrial, service, and retail area. Manufactures in the city include paper products, steel, and chemicals. The city, founded in 1849, is named for the biblical Antakya. Population 43,559 (1980); 62,195 (1990); 90,532 (2000).