Area codes 510 and 341 are

telephone A telephone is a telecommunications device that permits 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 efficiently the human voice, into el ...

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, re ...

s in the

North American Numbering Plan The North American Numbering Plan (NANP) is a 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 and has the international calling ...

(NANP) serving much of the East Bay in the U.S. state of

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

. They cover parts of Contra Costa County and western Alameda County, including the city of Oakland, but excluding

Dublin Dublin (; , or ) is the capital and largest city of Ireland. On a bay at the mouth of the River Liffey, it is in the province of Leinster, bordered on the south by the Dublin Mountains, a part of the Wicklow Mountains range. At the 2016 ...

, Livermore,

Pleasanton Pleasanton may refer to: Places * Pleasanton, California * Pleasanton, Iowa * Pleasanton, Kansas * Pleasanton, Nebraska * Pleasanton, New Mexico * Pleasanton, Ohio * Pleasanton, Texas * Pleasanton Township, Michigan Other * Pleasanton High School ...

, and Sunol. Area code 510 was established on September 2, 1991, in a split from area code 415. On March 4, 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.

Cities in the numbering plan area

Alameda County

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

Piedmont it, Piemontese , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = , demographics1_footnotes = , demographics1_title1 = , demographics1_info1 = , demographics1_title2 ...

* San Leandro *

San Lorenzo San Lorenzo is the Italian and Spanish name for Lawrence of Rome, Saint Lawrence, the 3rd-century Christian martyr, and may refer to: Places Argentina * San Lorenzo, Santa Fe * San Lorenzo Department, Chaco * Monte San Lorenzo, a mountain on t ...

* Union City

Contra Costa County

* Bayview-Montalvin *

Canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, 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 to cut ...

* 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 th ...

* Kensington * North Richmond * Pinole *

Port Costa Port Costa is a small village and census-designated place (CDP) in Contra Costa County, California, located in East Bay region of the San Francisco Bay Area. Situated on the southern shore of the Carquinez Strait, the population was 190 at the 2 ...

* Richmond * Rodeo * Rollingwood * San Pablo * Tara Hills

Introduction of 341

By 2016, the California Public Utilities Commission (CUPC) 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

Administrator (NANPA) proposed in May 2017 that CPUC relieve 510 by introducing the

overlay area code In telecommunications, an area code overlay complex is a telephone numbering plan that assigns multiple area codes to a geographic numbering plan area (NPA). Area code overlays are implemented in territories of the North American Numbering Pla ...

341 for the entire territory. NANPA had previously assigned 341 as the relief area code for 510 in 1999, but nationwide

number pooling Number pooling is a method of reallocating telephony numbering space in the North American Numbering Plan, primarily in growth areas in the United States. Instead of allocating blocks of ten thousand numbers to each carrier in each community, a bl ...

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; otherwise, a recorded message will remind them if they dial incorrectly.

Prior usage of 510 for TWX

In the United States,

AT&T AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile tel ...

originally used NPA 510 for the TWX ( TeletypeWriter eXchange) network.

Western Union The Western Union Company is an American multinational financial services company, headquartered in Denver, Colorado. Founded in 1851 as the New York and Mississippi Valley Printing Telegraph Company in Rochester, New York, the company ch ...

acquired the TWX network in 1969 and renamed it

Telex II The telex network is a station-to-station switched network of teleprinters similar to a telephone network, using telegraph-grade connecting circuits for two-way text-based messages. Telex was a major method of sending written messages electroni ...

. By the 1970s, three TWX codes had been added ( 710 in the Northeast, 810 in Michigan, Ohio, Indiana, Kentucky, North Carolina, South Carolina, Georgia, Florida, Louisiana, Mississippi, and Alabama; and 910 west of the

Mississippi Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Mis ...

). Each major city had one or more local exchange prefixes.Traffic Routing Guide
sec. 15-16, AT&T, 1975 Western Union upgraded the network to "4-row"

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because ...

operation (it previously used both "3-row" Baudot and ASCII transmission) and decommissioned the special TWX area codes in 1981. In Canada, TWX used 610 (nationwide) from 1962 until the remaining numbers were moved to

area code 600 Area code 600 is a telephone area code in the North American Numbering Plan for non-geographic use in Canada of specialized telecommunication services such as telex applications, caller-pays cellular, ISDN, and mobile satellite communication ...

in 1992.

References

External links

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