Area 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. state of California. They cover parts of Contra Costa County and western Alameda County, including the city of Oakland, but excluding Dublin, Livermore, Pleasanton, and Sunol.
Area code 510 was established on September 2, 1991, in a split from area code 415.[1] On March 14, 1998, the inland portion of the East Bay was split off as area code 925. 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.
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 first central office codes in 341 became available on July 22, 2019.[2][3] Ten-digit dialing became mandatory in the East Bay a month earlier, on June 22.[4]
- ^ "Archived copy" (PDF). Archived from the original (PDF) on 2011-06-04. Retrieved 2008-09-01.
{{cite web}}: CS1 maint: archived copy as title (link) - ^ Prosper, Terrie (June 21, 2018). "CPUC Provides More Numbers in 510 Area Code Region" (PDF) (Press release). California Public Utilities Commission. Retrieved June 21, 2018.
- ^ California Public Utilities Commission (June 21, 2018). "Decision Granting Request for an All-Service Area Code Overlay in the 510 Numbering Plan Area" (PDF). Retrieved June 21, 2018.
- ^ "341 Area Code, New Dialing Procedure Coming To Alameda, Contra Costa Counties". KPIX-TV. June 21, 2019.