The NANPA retained 341 for the then-future relief of 510.

NANPA had previously assigned 341 as the relief area code for 510 in 1999, but nationwide number pooling procedures eliminated the need at that time. The North American Numbering Plan Administrator (NANPA) proposed in May 2017 that CPUC relieve 510 by introducing the overlay area code 341 for the entire territory. In response, the commission held meetings in Berkeley, Oakland and Hayward in January and February 2017 to discuss area code relief for 510. īy 2016, the California Public Utilities Commission (CUPC) projected that NPA 510 would exhaust its numbering pool by the second quarter of 2019. Ten-digit dialing became mandatory in the East Bay a month earlier, on June 22. The first central office codes in 341 became available on July 22, 2019. In response to projections that 510 would exhaust in the second quarter of 2019, the California Public Utilities Commission approved the addition of an overlay area code, 341, to serve the East Bay. The dividing line followed the Berkeley Hills almost everything west of the hills stayed in 510, while everything east of the hills transferred to 925. On March 4, 1998, the inland portion of the East Bay was split off as area code 925. They cover parts of Contra Costa County and western Alameda County, including the city of Oakland, but excluding Dublin, Livermore, Pleasanton, and Sunol.Īrea code 510 was established on September 2, 1991, in a split from area code 415. Area code 510 is shown in red.Īrea codes 510 and 341 are telephone area codes in the North American Numbering Plan (NANP) serving much of the East Bay in the U.S. Numbering plan areas in California (blue) and border states.

State of california 2016 extension form