Area codes 510 and 341 are

telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...

area code A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, rea ...

s in the

North American Numbering Plan The North American Numbering Plan (NANP) is an integrated telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1, World Numbering Zone ...

(NANP) serving much of the

East Bay The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa counties. Wi ...

in the U.S. state of

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. They cover parts of

Contra Costa County Contra Costa County (; ''Contra Costa'', Spanish language, Spanish for 'Opposite Coast') is a U.S. county, county located in the U.S. state of California, in the East Bay of the San Francisco Bay Area. As of the 2020 United States census, the ...

and western Alameda County, including the city of Oakland, but excluding

Dublin Dublin is the capital and largest city of Republic of Ireland, Ireland. Situated on Dublin Bay at the mouth of the River Liffey, it is in the Provinces of Ireland, province of Leinster, and is bordered on the south by the Dublin Mountains, pa ...

, Livermore, Pleasanton, and Sunol. Area code 510 was established on September 2, 1991, in a split from area code 415. 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. Ten-digit dialing became mandatory in the East Bay a month earlier, on June 22.

History

Introduction of 341

By 2016, the California Public Utilities Commission (CPUC) projected that NPA 510 would exhaust its numbering pool by the second quarter of 2019. In response, the commission held meetings in Berkeley, Oakland and Hayward in January and February 2017 to discuss area code relief for 510. The North American Numbering Plan Administrator (NANPA) proposed in May 2017 that the CPUC to overlay the numbering plan area with area code 341. NANPA had previously assigned 341 as the relief area code in 1999, but nationwide

number pooling Telephone number pooling, thousands-block number pooling, or just number pooling, is a method of allocating telephony numbering space of the North American Numbering Plan in the United States. The method allocates telephone numbers in blocks of 1,0 ...

procedures eliminated the need at that time. The NANPA retained 341 for the then-future relief of 510. CPUC accepted the NANPA proposal in a decision on June 21, 2018. With the start of the overlay plan in July 2019, all customers in the numbering plan area can be assigned telephone numbers with either code, and must dial the area code for all calls.

Prior usage of 510 for TWX

In 1962,

AT&T AT&T Inc., an abbreviation for its predecessor's former name, the American Telephone and Telegraph Company, is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the w ...

assigned NPA 510 for conversion to dial service of the Teletypewriter Exchange Service (TWX) in the United States.Traffic Routing Guide
sec. 15-16, AT&T, 1975 Telex use of area code 510 was decommissioned in 1981 after conversion of the service to new transmission technologies by Western Union,

Service area

The service area contains the following cities in two counties.

Alameda County

* Alameda * Albany * Ashland * Berkeley * Castro Valley * Cherryland * Emeryville * Fairview * Fremont * Hayward * Newark * Oakland *

Piedmont Piedmont ( ; ; ) is one of the 20 regions of Italy, located in the northwest Italy, Northwest of the country. It borders the Liguria region to the south, the Lombardy and Emilia-Romagna regions to the east, and the Aosta Valley region to the ...

* San Leandro * San Lorenzo * Union City

Contra Costa County

* Bayview *

Canyon A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...

* Crockett * East Richmond Heights * El Cerrito * El Sobrante *

Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the Gr ...

Kensington Kensington is an area of London in the Royal Borough of Kensington and Chelsea, around west of Central London. The district's commercial heart is Kensington High Street, running on an east–west axis. The north-east is taken up by Kensingt ...

* Montalvin Manor * North Richmond * Pinole * Port Costa * Richmond *

Rodeo Rodeo () is a competitive equestrian sport that arose out of the working practices of cattle herding in Spain and Mexico, expanding throughout the Americas and to other nations. It was originally based on the skills required of the working vaqu ...

* Rollingwood * San Pablo * Tara Hills

References

External links

{{coord, 37.7, N, 122.1, W, display=title 510 510 Northern California