antioch,_california | postalcode | 94509, 94531 <tsp> antioch,_california | areacode | 925 <tsp> antioch,_california | areatotal | 75324 (square kilometres) <sep> antioch is the third-largest city in contra costa county, california, united states the city is located in the east bay region of the san francisco bay area along the sacramento–san joaquin river delta the city's population was 115,291 at the 2020 census the city has grown substantially more diverse since the 1970s 
antioch has the total area of 75.324 square km and is located within california. its postal codes are 94509 and 94531 while the area code is 925.no information