520 Area Code – Tucson, Arizona: Location, Time Zone & History

Area code 520 traces to March 19, 1995, when it split from the original Arizona code 602 to serve rural and southern Arizona outside metropolitan Phoenix; mandatory dialing followed that October, with Tucson converting on December 31, 1996. A second reorganization came in February 2001, when the Arizona Corporation Commission approved carving out area code 928 for the northern, eastern, and western reaches of the former footprint, leaving Cochise, Pima, Pinal, and Santa Cruz counties on the code. The new code entered service June 23, 2001, mandatory from January 5, 2002. Ten-digit dialing became mandatory on October 24, 2021, tied to the introduction of the 988 crisis line. Despite these changes, the region has never needed an overlay, remaining a single numbering plan area distinct from the merged overlay serving Phoenix to the north.

Tucson anchors the territory, with service extending to Sierra Vista, Casa Grande, Nogales, Bisbee, Douglas, Benson, Green Valley, Marana, and Oro Valley. The local economy spans optics and photonics manufacturing centered on the University of Arizona's College of Optical Sciences, aerospace and defense work tied to Davis-Monthan Air Force Base and Raytheon/RTX missile systems, copper mining in Cochise and Pinal counties, and border trade and agriculture around Nogales. Dark skies support astronomy at Kitt Peak and nearby observatories. Tucson was named the first UNESCO City of Gastronomy in the United States on December 15, 2015, recognizing four millennia of local culinary tradition; the state, outside the Navajo Nation, skips daylight saving time.