Area Code Atlas

NPA 510 assigned for TWX service

In 1962, area code 510 was assigned as a Service Access Code (SAC) for the conversion to dial service of the Teletypewriter Exchange Service (TWX) in the United States.

NPA 510 assigned for TWX service

Area code 510 was assigned in 1962 as a Service Access Code for the conversion to dial service of the Teletypewriter Exchange Service (TWX) in the United States.

Area code 510 assigned for TWX service

Area code 510 was assigned in 1962 by AT&T for conversion to dial service of the Teletypewriter Exchange Service (TWX) in the United States. This use was decommissioned in 1981 after conversion of the service to new transmission technologies by Western Union.

NPA 510 assigned for TWX service

Area code 510 was assigned in 1962 for conversion to dial service of the Teletypewriter Exchange Service (TWX) in the United States. This use was decommissioned in 1981 after conversion to new transmission technologies.

Traffic Routing Guide issued

The Traffic Routing Guide, which included information on TWX area codes such as 510 and 810, was issued on November 29, 1965.

Traffic Routing Guide revised and issued

A revised edition of the Traffic Routing Guide, covering TWX area codes including 510 and 810, was issued on September 12, 1975.

NPA 510 split from 415

Area code 510 was created in 1991 as a split from 415 to serve most of the East Bay region of California, including cities such as Oakland and Berkeley.

NPA 510 split from 415 for the East Bay in 1991

On September 2, 1991, area code 510 was created for the East Bay, including Oakland, splitting from area code 415 to address growing demand for telephone numbers in the region. 415 continued to serve San Francisco and Marin County.

Announcement of Jeopardy Procedures for 510 and 916 NPAs (California)

NANP- Split of 510 (California) Numbering Plan Area (NPA)

NPA 925 split from 510

Area code 925 was created on March 14, 1998, when area code 510 was split along the natural border of the Berkeley Hills. The new code covered the inland portions of the East Bay, including southeastern Alameda County and most of Contra Costa County.

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

Suspension of overlay relief for 408 and other NPAs

On December 16, 1999, the California Public Utilities Commission suspended the implementation of planned overlays for area codes 408, 415, 510, 650, 714, and 909. This action was taken due to the adoption of telephone number pooling, which delayed the need for additional area codes.

Overlays Suspended in the 408, 415, 510, 650, 714 & 909 NPAs

NPA 510 (California) - Relief Plan Dismissed

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.