510 Area Code

On June 21, 2018, the California Public Utilities Commission (CPUC) adopted Decision 18-06-013, approving an overlay that will add the new 341 area code to the geographic region served by the 510 area code. The overlay will allow existing 510 area code customers to keep their telephone numbers and area code. However, as of June 22, 2019, all calls made from 510 area code numbers must be completed by dialing 1 + area code + 7-digit telephone number. Calls that are dialed without the “1” and the area code will not be completed and will result in a recording instructing the caller to hang up and dial again. Cellphone callers who have service with certain cell service providers may be able to complete calls without dialing “1” before the area code. Beginning July 22, 2019, new telephone lines or services may be assigned numbers with the 341 area code, depending on telephone number availability. All calls made from 341 area code numbers must also be dialed as 1 + area code + 7-digit telephone number.

Dialing 1 + area code + 7-digit telephone number does not change what a call costs and does not mean that a call is a toll or long distance call. Therefore, calling areas and rates will not change. What is a local call before the overlay will remain a local call after the overlay and dialing “1” and the area code does not mean there will be a charge for the call. Calls to 911, as well as 211, 311, 411, 511, 611, 711 and 811 will not be affected, and will continue to be dialed with 3 digits.


On May 19, 2017, the North American Numbering Plan Administrator (NANPA) filed Application 17-05-013 with the CPUC to add a new area code via overlay to the geographic area currently served by the 510 area code, due to the projected depletion of 510 prefixes by the 2nd quarter of 2019.

CPUC held public meetings on January 17 and February 15, 2017 in Oakland, Berkeley and Hayward. At the meetings, NANPA presented the overlay and split options for adding a new area code to the 510. Attendees asked questions and expressed their opinions at the public meetings, and were further provided an opportunity to submit written comments to the CPUC. Public comments were also submitted via email and postal mail to the CPUC Public Advisor’s Office. Majority of the public comments indicate support for an overlay as an overlay allows existing 510 customers to keep the same area code and telephone number; an overlay also has minimal impact on local government and emergency services.

The 510 area code was created when it was split off of the 415 area code in September 1991. The 510 area code was split again when the 925 area code was split off in 1998. The area served by the 510 area code comprises the western portions of Alameda and Contra Costa Counties. The 510 area code serves the cities of Alameda, Albany, Berkeley, Emeryville, Fremont, Hayward, Newark, Oakland, Piedmont, San Leandro and Union City in Alameda County; and the cities of El Cerrito, Hercules, Pinole, Richmond, and San Pablo in Contra Costa County. The 510 area code is bordered on the north by the 707 area code, directly to the west by the San Francisco Bay and then further west by the 415/628 area code overlay complex and the 650 area code; to the east by the 925 area code and to the south by the 408/669 area code overlay complex.

Questions and comments concerning the 510/341 area code overlay may be submitted to the Public Advisor’s Office by:

• Email to public.advisor@cpuc.ca.gov, or

• Postal mail to CPUC Public Advisor’s Office, 320 W. 4th Street, Suite 500, Los Angeles, CA 90013.

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