It was one of the original area codes established in October 1947 and originally covered the entire state of Arizona until 1995, when area code 520 was established as the state's second area code. Arizona's explosive population growth during the second half of the 20th century would have made a split necessary in any event. However, the increased demand for telephone lines created by the proliferation of fax machines, cell phones and dial-up Internet connections brought the state's number pool close to exhaustion by the early 1990s. Many states introduced new area codes during this time frame for much the same reason. Generally, greater Phoenix retained 602, except for some outer portions of Maricopa County that transferred to 520.
The creation of 520 was intended as a long-term solution. Within only three years, however, 602 came close to exhaustion once again due to the Valley of the Sun's continued dramatic growth and the continued proliferation of cell phones and pagers. It was eventually decided that the Valley of the Sun needed multiple area codes. Initially, plans called for an overlay of 602 with another area code. However, overlays were a new concept at the time, and met with some resistance due to the requirement for ten-digit dialing and the fact that overlays make the location of phone numbers ambiguous.
As a result, a three-way geographic split was chosen instead. The split became effective on April 1, 1999. The eastern portion, from the Town of Paradise Valley (which goes as far west as 32nd St) as well as the city north of Union Hills and east of the 2000 E Grid, and everything from about 56th Street eastward, became 480. Most of the western portion, including the city west of 39th Ave north of Indian School to west of 63rd Ave from I-10 south, along with the city from north of Union Hills and west of the 2000 E Grid, became 623.
Generally, 480 served the East Valley, while 623 served the West Valley. Most areas of Phoenix remained in 602, but a few areas (such as the Ahwatukee neighborhood and parts of Maryvale) transferred to 480 or 623. The area code divider between 602 and 623 was drawn in such a manner that in some neighborhoods, homes only a few hundred feet away from each other may have different area codes. Glendale's northern half has the area code divider running diagonally through its middle. A small portion of Tempe (west and south of the I-10 Broadway Curve) also remained in 602.
This split resulted in Phoenix becoming one of the few major cities in the nation to be split between multiple area codes. Only two cities ended with multiple area codes with this change. While this also made Phoenix one of the few major cities not to be overlaid, ten-digit dialing is now necessary in certain areas of the metro area. And it is the only million-plus populated area where 7-digit dialling would still be possible.
|Arizona area codes: 480, 520, 602, 623, 928|
|West: 623||area code 602||East: 480|
|South: 480, 520|