Area Code Atlas

NANP- Overlay of 510 Numbering Plan Area (NPA) with 341 NPA - California

Overlay relief planned for area code 510 with new code 341

The North American Numbering Plan Administrator proposed on May 19, 2017, an overlay complex for the 510 numbering plan area with new area code 341 to address projected number exhaustion.

CPUC approves 341 overlay for 510

On June 21, 2018, the California Public Utilities Commission approved an all-services overlay for the 510 area code region, introducing area code 341 to provide additional numbering resources as 510 approached exhaustion. The overlay was implemented to address the projected exhaustion of available prefixes in the 510 area code by mid-2019.

CPUC approves overlay of 341 on 510

The California Public Utilities Commission accepted the relief plan for an all-service overlay of area code 341 on the 510 numbering plan area to address number exhaustion.

NPA 341 overlay on 510 announced

NPA 341 to Overlay 510 (California)

Permissive 1+10-digit dialing begins for 510/341

Permissive 1+10-digit dialing began on December 15, 2018, for the 510 and new 341 area codes. During this period, callers could use either 7-digit or 1+10-digit dialing for local calls within the overlay region.

Mandatory 1+10-digit dialing for 510/341

On June 22, 2019, mandatory 1+10-digit dialing was implemented in the East Bay region for both the 510 and 341 area codes. All local calls now required dialing the area code plus the seven-digit number.

NPA 341 overlay activated for 510

On July 22, 2019, area code 341 was activated as an overlay for the 510 area code region. New central office codes in 341 became available, and customers in the region could be assigned numbers with either code.