510/341 Area Code

On June 21, 2018, the California Public Utilities Commission (CPUC) approved an overlay in Decision 18-06-013 to accommodate the need for additional telephone numbers in the geographic region served by the 510 area code. On July 22, 2019, the overlay became effective and the 341 area code was overlaid onto the 510 area code.

The overlay allows existing 510 area code customers to keep their telephone numbers and the 510 area code. However, calls made from the 510 and the 341 area codes need to be dialed as 1 + area code + 7-digit telephone number. Calls placed from 510 or 341 numbers 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 complete calls without dialing “1” before the area code.

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 do not change. What is a local call before the overlay remains a local call after the overlay and dialing “1” and the area code does not mean there is a charge for the call. Calls to 911, as well as 211, 311, 411, 511, 611, 711 and 811 are not be affected, and continue to be dialed with 3 digits.


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. Today, the 510 area code and its overlay area code 341 serve the western portions of Alameda and Contra Costa Counties. The 510 and the 341 area codes serve 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 510/341 area code overlay complex 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.

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