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Area code 520
Area code 520
Area code 520
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Area code 435Area code 970Area code 505Area code 575Area code 775Area codes 702 and 725Area codes 760 and 442Telephone numbers in MexicoArea code 520Area code 928Area codes 602, 480, and 623
Clickable map of Arizona area codes in blue (and border states) with area code 520 shown in red

Area code 520 is a telephone area code in the North American Numbering Plan (NANP) for the U.S. state of Arizona. The numbering plan area comprises Tucson and most of the southeastern part of the state.

Area code 520 was created in a split of area code 602 on March 19, 1995. Previously, 602 had been the sole area code for the entire state of Arizona since the introduction of area codes in 1947. Arizona's rapid growth in demand for telecommunication services during the second half of the 20th century, and the proliferation of mobile and data communication services in the 1990s required additional numbering resources. The numbering plan area originally comprised all of the state outside the Phoenix metropolitan area, but areas outside of southeastern Arizona were split again in 2001 to form area code 928 in 2001.

History

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Area code 602 was the only area code for Arizona from the establishment of a nationwide telephone numbering plan in 1947. By the late 1980s, the state needed a second area code to satisfy population growth and increased demand for telephone numbers. Mountain Bell, the incumbent local exchange carrier in the state, requested a second area code for Arizona in 1988.[1] BellCore, which at the time administered the assignment of area codes, denied Mountain Bell's request and instead placed Arizona into the first phase of interchangeable dialing, in which central office codes with a middle digit of 0 or 1 were made available for use, in 1990.[2] This meant that in-state toll and collect calls would require dialing the area code.[3]

By the early 1990s, Arizona was one of the largest states served by only one area code, and it was apparent that the immediate need for a second area code could no longer be staved off. In advance of the 1995 introduction of interchangeable area codes (area codes with a middle digit not 0 or 1), and in response to continued population growth, Arizona was allocated a second area code, area code 520. The new area code completely surrounded metropolitan Phoenix, which mostly retained 602.[4] 520 was introduced on March 19, 1995. Permissive dialing of 602 continued across Arizona until October 22, 1995. On that date, use of 520 became mandatory for rural Arizona. The new area code became mandatory in Flagstaff, Prescott, and Yuma on June 30, 1996, and in Tucson on December 31, 1996. The freed central office codes in 602 were then used for new telephone numbers in the Phoenix area.[5]

Continued line demand in Arizona outside of metropolitan Phoenix, however, necessitated a second split of 520. In 2000, the Arizona Corporation Commission, which regulates public utilities, began to discuss its options. The telecommunications industry favored a split similar to that eventually adopted but moving Cochise County into the new area code.[6] The eventual split approved by the commission in February 2001 kept Cochise, Pima, Pinal, and Santa Cruz counties in 520 while the new area code, area code 928, was assigned to the remainder of the former 520 area.[7] (Some areas of Pinal County are in 480, while the Gila River Indian Community, which extends into Maricopa County, is in 520.[8]) Permissive dialing of 928 began in July 2001 and ended on January 5, 2002.[9]

Prior to October 2021, area code 520 had telephone numbers assigned for the central office code 988. In 2020, 988 was designated nationwide as a dialing code for the National Suicide Prevention Lifeline, which created a conflict for exchanges that permit seven-digit dialing. This area code was therefore scheduled to transition to ten-digit dialing by October 24, 2021.[10]

Service area

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Counties

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Municipalities

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See also

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References

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Area code 520

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from Grokipedia
Area code 520 is a area code in the serving southeastern in the United States, primarily covering the Tucson metropolitan area and surrounding regions. It was established on March 19, 1995, as a split from the original Arizona area code 602 to address the exhaustion of available telephone numbers due to and increased demand in the state. It was further split in 2001 to create for northern and western portions of its original territory. The area code encompasses a diverse geographic region in southern Arizona, including Pima County (home to Tucson, the second-largest city in the state), Cochise County, Santa Cruz County, and portions of Pinal County. Key cities served include Tucson (population 542,629 as of 2020), Sierra Vista, Nogales, Casa Grande, Oro Valley, Marana, and Douglas, supporting a total population of approximately 1.3 million residents (as of 2023 estimates) across urban, rural, and border communities.[](https://www.census.gov/quickfacts/fact/table/pimacountyarizona,PIMAAZ%2Ccochise countyarizona,santacruzcountyarizona) This region features a mix of cultural landmarks, such as the in Tucson, natural attractions like the , and economic hubs focused on education, tourism, mining, and cross-border trade with . Area code 520 operates without an overlay, requiring 10-digit local dialing since October 24, 2021, in line with guidelines for all area codes to facilitate future expansion. It falls within the Mountain Standard Time zone (UTC−7), with observing permanent without except in the portion. As of 2025, no immediate relief planning is underway, though the area code manages 689 active prefixes with high utilization, reflecting steady growth in needs for local businesses, residents, and emerging technologies like VoIP services.

History

Creation from Area Code 602

Area code 602 was established in 1947 as one of the original 86 area codes in the , initially covering the entire state of . Arizona's population surged during the late , particularly from the onward, with the state averaging a four percent annual growth rate in the Phoenix area alone over four decades, driving increased demand for telephone services and leading to the near exhaustion of available numbers in area code 602 by the early . To alleviate this pressure, the North American Numbering Plan Administration approved a split of area code 602, creating area code 520 for the southeastern portion of the state, with the new code entering service on March 19, 1995. Upon its introduction, area code 520 served all of Arizona outside the Phoenix metropolitan area, including rural and southern regions such as Tucson and surrounding communities. The split required the transition to ten-digit dialing in the affected rural areas outside major cities, beginning with permissive dialing on March 19, 1995, where both seven-digit and ten-digit formats were accepted using either area code; this period lasted through much of 1995, after which mandatory with 520 became required for calls within the new service area.

Split to Create Area Code 928

By the early 2000s, area code 520 was nearing exhaustion of its supply of available telephone numbers, driven by sustained population growth and expanding telecommunications demand across Arizona following its creation in 1995. To address this shortage, the Arizona Corporation Commission approved a geographic split of area code 520 in February 2001, establishing the new area code 928 for northern and western portions of the state. The split boundaries were chosen to keep the more populous southeastern counties in 520 while assigning less dense northern and western areas to 928. The split's permissive dialing period began on June 23, 2001, allowing calls to be completed using either 520 or 928 in the transition zones, with mandatory use of the appropriate area code required starting January 5, 2002. This reconfiguration reassigned key communities including Flagstaff, Prescott, Yuma, and Kingman—along with surrounding rural and border areas in the north and west—to the 928 overlay, relieving pressure on the original code. Consequently, area code 520's footprint contracted to encompass only southeastern , centering on Tucson and adjacent border counties such as Pima, Pinal, , and Santa Cruz.

Transition to Ten-Digit Dialing

Following the creation of area code 520 from area code 602 in 1995, a permissive dialing period allowed callers to use either area code for local calls within the new region. Mandatory 1+ area code dialing was phased in over the next 18 months, starting with rural areas on October 22, 1995, followed by Flagstaff, Prescott, and Yuma on June 30, 1996, and concluding in Tucson on December 31, 1996. In 2020, the designated 988 as the nationwide three-digit code for the Suicide and Crisis Lifeline, necessitating a shift to ten-digit dialing in area codes where 988 was already in use as a seven-digit local exchange code to prevent conflicts. This nationwide initiative affected over 80 area codes, including Arizona's , 520, and 928. For area code 520, a permissive period began in April 2021, allowing callers to use either seven- or ten-digit formats for local calls. Mandatory took effect on October 24, 2021, requiring all local calls within the 520 region to include the area code plus the seven-digit number. The transition impacted residents and businesses across , prompting updates to automatic dialing systems, contact lists, medical equipment, alarm services, and printed directories to ensure seamless local connectivity. Seven-digit local calls placed after the deadline were rerouted with an intercept message instructing users to redial with ten digits. As of 2025, area code 520 is projected to exhaust in the first quarter of 2027, with no relief measures such as an overlay planned as of 2025.

Service Area

Counties Covered

Area code 520 provides telephone service to four primary counties in southeastern , encompassing a diverse region that includes urban centers, rural areas, and border communities. These counties are , Pima, Pinal, and Santa Cruz, with coverage spanning over 20,000 square miles in total land area. Portions of Graham County, previously included, were reassigned to following the 2002 split. Cochise County receives full coverage under area code 520, including its border towns along the U.S.- line. The county has a population of approximately 125,773 as of the 2024 U.S. estimate. Pima County forms the core of the 520 service area, centered on its primary urban hub, and is the largest county served by this code with over 1 million residents. Its population stands at 1,080,149 according to the 2024 U.S. estimate. Pinal County has partial coverage, primarily in its southern portions, while northern areas fall under area code 480. This includes the , which extends into adjacent Maricopa County but retains 520 numbering. The county's overall population is 513,862 per the 2024 U.S. estimate. Santa Cruz County is fully covered by area code 520 and lies along the U.S.- border, making it the smallest county in the service area with a of around 50,508 as of the 2024 U.S. Census estimate.

Cities and Towns Served

Area code 520 primarily serves , encompassing a diverse array of urban centers, suburban communities, and rural towns across several counties. The largest city within this area code is Tucson, the of Pima County and a major economic and cultural hub known for its , , and industries, with a of 547,232 as of 2023. Other significant municipalities include Sierra Vista in Cochise County, a military-oriented town adjacent to that supports defense-related activities, with a population of 45,203 in 2023; and Casa Grande in Pinal County, a rapidly growing suburban area with agricultural and manufacturing ties, home to about 57,590 residents that year. Northern suburbs of Tucson, such as Marana and Oro Valley in Pima County, contribute to the region's residential expansion; Marana, focused on logistics and development, had 54,487 people in 2023, while Oro Valley, emphasizing retail and recreation, counted 47,595. Nogales, a in Santa Cruz County serving as a vital international trade port with , has a population of 19,753 as of 2023. Additional notable towns highlight the area's historical, rural, and border dynamics. These include Bisbee in County, a historic town with cultural preservation efforts and a population of around 4,800; Benson in the same county, a former rail hub now supporting tourism, with about 5,000 residents; Sahuarita in Pima County, an expanding community driven by residential growth, home to roughly 34,000 people; Douglas in Cochise County, a border area with mining heritage and approximately 16,000 inhabitants; and Arizona City in Pinal County, a rural retirement spot with nearly 11,000 residents. The area code also covers unincorporated regions and Native American communities, such as the Tohono O'odham Nation in Pima and Pinal Counties, which spans vast desert lands and integrates traditional governance with modern services.

References

  1. https://www.allareacodes.com/520
  2. https://www.areacodelocations.info/5/520.html
  3. https://arizona.phonenumbers.org/520-area-code/
  4. https://www.census.gov/quickfacts/fact/table/pinalcountyarizona
  5. https://www.letsdial.com/blog/520-area-code/
  6. http://www.azcc.gov/utilities/industry-types/telephone/all-about-area-codes
  7. https://www.teloz.com/blog/520-area-code/
  8. https://www.allareacodes.com/602
  9. https://www.dingtone.me/area-code/602-phone-number.html
  10. https://www.sent.dm/resources/area-code-602-phoenix-arizona
  11. https://www.vitelglobal.com/local-numbers/arizona/520-area-code
  12. https://www.azcentral.com/story/news/local/asked-answered/2015/05/07/asked-answered-valleys-area-codes-evolved-cbt/70919962/
  13. https://www.sent.dm/resources/area-code-520-casa-grande-arizona-guide
  14. https://www.narpm.org/docs/members/magazine/1995/1995march.pdf
  15. https://www.myheraldreview.com/keeping-520/article_1fd15137-57b8-5fc8-9fc3-2892fab96631.html
  16. https://www.gvnews.com/new-928-area-code-makes-debut-saturday-in-arizona/article_8f9cf238-d145-5aab-bf5f-327e0426c818.html
  17. https://docs.fcc.gov/public/attachments/DOC-371188A2.pdf
  18. https://www.fox10phoenix.com/news/10-digit-dialing-to-be-required-in-some-arizona-area-codes1
  19. https://it.arizona.edu/news/fcc-requires-10-digit-dialing-starting-october-24
  20. https://tucson.com/news/local/a-big-change-is-coming-for-the-way-you-make-local-phone-calls-in-tucson/article_b09da91d-bf45-576d-b339-63f9e301ede1.html
  21. https://www.centurylink.com/notifications/10_digit_dialing/arizona.html
  22. https://www.zip-codes.com/area-code/area-code-520.asp
  23. https://www.nanpa.com/sites/default/files/2025-04/2025-1NPAExhaustProjectionsFinal.pdf
  24. https://censusreporter.org/profiles/16000US0477000-tucson-az/
  25. https://censusreporter.org/profiles/16000US0466820-sierra-vista-az/
  26. https://censusreporter.org/profiles/16000US0410530-casa-grande-az/
  27. https://censusreporter.org/profiles/16000US0444270-marana-az/
  28. https://censusreporter.org/profiles/16000US0451600-oro-valley-az/
  29. https://censusreporter.org/profiles/16000US0449640-nogales-az/
  30. https://24timezones.com/520/area-code
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