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 e ...

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

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 m ...

. They cover parts of Contra Costa County and western

Alameda County Alameda County ( ) is a county located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. Alam ...

, 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 c ...

, Livermore, Pleasanton, and Sunol. Area code 510 was established on September 2, 1991, in a split from

area code 415 Area codes 415 and 628 are telephone area codes in the North American Numbering Plan (NANP) for the city of San Francisco and its northern suburbs in Marin County (across the Golden Gate), and the northeast corner of San Mateo County in the U.S. ...

. On March 4, 1998, the inland portion of the East Bay was split off as

area code 925 Area code 925 is a telephone area code that was split from area code 510 in the U.S. state of California, on March 14, 1998. It covers the inland portions of the East Bay counties of Alameda and Contra Costa in the northern area of California. T ...

. The dividing line followed the

Berkeley Hills The Berkeley Hills are a range of the Pacific Coast Ranges that overlook the northeast side of the valley that encompasses San Francisco Bay. They were previously called the "Contra Costa Range/Hills" (from the original Spanish ''Sierra de la ...

; 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 The California Public Utilities Commission (CPUC or PUC) is a regulatory agency that regulates privately owned public utilities in the state of California, including electric power, telecommunications, natural gas and water companies. In addition ...

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 Ten-digit dialing is a telephone dialing procedure in the countries and territories that are members of the North American Numbering Plan (NANP). It is the practice of including the area code of a telephone number when dialing to initiate a telep ...

became mandatory in the East Bay a month earlier, on June 22.

Cities in the numbering plan area

Alameda County

Alameda An alameda is a Avenue (landscape), street or path lined with trees () and may refer to: Places Canada *Alameda, Saskatchewan, town in Saskatchewan **Grant Devine Dam, formerly ''Alameda Dam'', a dam and reservoir in southern Saskatchewan Chile ...

* Albany * Ashland *

Berkeley Berkeley most often refers to: *Berkeley, California, a city in the United States **University of California, Berkeley, a public university in Berkeley, California * George Berkeley (1685–1753), Anglo-Irish philosopher Berkeley may also refer ...

Castro Valley Castro Valley is a census-designated place (CDP) in Alameda County, California, United States. At the 2010 census, it was the fifth most populous unincorporated area in California and the twenty-third most populous in the United States. The popula ...

* Cherryland *

Emeryville Emeryville may refer to: * Emeryville, California Emeryville is a city located in northwest Alameda County, California, in the United States. It lies in a corridor between the cities of Berkeley and Oakland, with a border on the shore of San ...

* Fairview * Fremont * Hayward *

Newark Newark most commonly refers to: * Newark, New Jersey, city in the United States * Newark Liberty International Airport, New Jersey; a major air hub in the New York metropolitan area Newark may also refer to: Places Canada * Niagara-on-the ...

* Oakland *

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

San Leandro San Leandro (Spanish for " St. Leander") is a city in Alameda County, California, United States. It is located in the East Bay of the San Francisco Bay Area; between Oakland to the northwest, and Ashland, Castro Valley, and Hayward to the sout ...

* San Lorenzo * Union City

Contra Costa County

* Bayview-Montalvin * Canyon *

Crockett Crockett may refer to: People and fictional characters *Crockett Gillmore (born 1991), American National Football League player *Crockett Johnson, pen name of David Johnson Liesk (1906-1975), American cartoonist and children's book illustrator *C ...

* 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 ...

* Kensington * North Richmond *

Pinole Pinole, also called pinol or pinolillo, is roasted ground maize, which is then mixed with a combination of cocoa, agave, cinnamon, chia seeds, vanilla, or other spices. The resulting powder is then used as a nutrient-dense ingredient to make d ...

* Port Costa *

Richmond Richmond most often refers to: * Richmond, Virginia, the capital of Virginia, United States * Richmond, London, a part of London * Richmond, North Yorkshire, a town in England * Richmond, British Columbia, a city in Canada * Richmond, California, ...

* Rodeo * Rollingwood * San Pablo * Tara Hills

Introduction of 341

By 2016, the

(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 te ...

originally used NPA 510 for the TWX (

TeletypeWriter eXchange 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 ...

) 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 cha ...

acquired the TWX network in 1969 and renamed it Telex II. By the 1970s, three TWX codes had been added (

710 __NOTOC__ Year 710 ( DCCX) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. The denomination 710 for this year has been used since the early medieval period, when the Anno Domini calendar er ...

in the Northeast,

810 __NOTOC__ Year 810 ( DCCCX) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. Events By place Byzantine Empire * Spring – The Venetian dukes change sides again, submitting to Ki ...

in Michigan, Ohio, Indiana, Kentucky, North Carolina, South Carolina, Georgia, Florida, Louisiana, Mississippi, and Alabama; and

910 Year 910 ( CMX) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. __NOTOC__ Events By place Europe * June 12 – Battle of Augsburg: The Hungarians defeat the East Frankish army under ...

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. Miss ...

). 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 ser ...

in 1992.

References

External links

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