Area Code 925 History:
Area code 925 was put into service. Area code 925 was created from a split of area code 510.
Counties in California within area code 925 include:
Alameda County, and Contra Costa County.
Major cities or places in California within area code 925 include:
Area code 925 serves portions of the East Bay region in Almeda and Contra Costa counties, including the larger cities and communities of Antioch, Bay Point, Brentwood, Concord, Danville, Dublin, Lafayette, Livermore, Martinez, Oakley, Pittsburg, Pleasant Hill, Pleasanton, San Ramon, and Walnut Creek in addition to many smaller communities within the area code 925 service area.