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# Arizona Area Code 520
The 520 area code serves southern Arizona, encompassing major cities including Tucson, the state's second-largest metropolitan area. This region covers approximately 30,000 square miles and includes diverse communities such as Sierra Vista, Nogales, and Casa Grande. The 520 area code was established in 1995 as a split from the original 602 area code, which previously covered the entire state. Today, 520 represents a significant portion of Arizona's population and economy, particularly the southern and southeastern regions of the state, and remains one of the largest geographic area codes by land area in the North American Numbering Plan.
The North American Numbering Plan (NANP) is a standardized system that assigns three-digit area codes to geographic regions across North America, enabling efficient telephone routing and communication infrastructure. Area codes are designated by the North American Numbering Plan Administration (NANPA), which operates under the oversight of the International Telecommunication Union. The system uses a hierarchical numbering structure where the first digit, middle digit, and last digit of an area code follow specific rules to optimize network management and prevent conflicts. When regions experience population growth or increased telecommunications demand, as Arizona did in the 1990s, NANPA authorizes the creation of new area codes through geographic splits or overlays, ensuring that telephone numbers remain available and the system continues to function efficiently for all users.