623 Area Code – Glendale, Arizona: Location, Time Zone & History

Area code 602 originally covered all of Arizona, and its breakup unfolded in stages. Rural and southern Arizona split off first, becoming area code 520 in 1995. Then, on March 1, 1999, a three-way split divided the remaining Phoenix metro itself: 602 stayed with central Phoenix, 480 was created for the East Valley, and 623 was created for the West Valley, taking in Glendale, Peoria, Surprise, Avondale, Goodyear, and the Sun City communities. Nearly a quarter-century later, on September 12, 2023, the boundaries separating 602, 480, and 623 were eliminated altogether, merging the three into a single overlay complex spanning Maricopa County with mandatory ten-digit dialing.

That milestone reflects how thoroughly the West Valley has grown into its own identity within the Phoenix area, distinct from the older 602 core and the East Valley's 480. Glendale hosts State Farm Stadium, home of the Arizona Cardinals, along with Desert Diamond Arena and the Westgate Entertainment District, while Luke Air Force Base, the world's largest F-35 training base, sits nearby as a defense and aerospace anchor. Sun City and Sun City West, meanwhile, built the area's reputation for retirement communities and healthcare, and Peoria, Surprise, Litchfield Park, El Mirage, and Youngtown round out a numbering area now also drawing data center development.