Numbering plan areas in California (blue) and border states. This map is clickable; click on any region shown to visit the page for those area codes.Area code 925 is shown in red.
The numbering plan area (NPA) was originally served with area code 415, one of the first three area codes of California in 1947, which originally was assigned to central California. In 1991, area code 510 was created to serve most of the East Bay. Area code 925 was created March 14, 1998, when area code 510 was split along the natural border of the Berkeley Hills.
The numbering plan area includes southeastern Alameda County (Dublin, Pleasanton, Livermore, Sunol, and unincorporated areas surrounding those communities), and all of Contra Costa County except the western part (El Cerrito to Crockett).
