n area code 602 is a state of Arizonatelephone area code that covers most of the city ofPhoenix. 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 soon became apparent that the Valley 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 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. This split resulted in Phoenix becoming one of the fewmajor cities in the nation to be split between multiple area codes. Most of Phoenix remained in 602, but a few areas 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. Only two cities ended with multiple area codes with this change. Glendale's northern half has the 602/623 border running diagonally through its middle. A small portion of Tempe also remained in 602, with most of the city moving to 480. Even with Phoenix's continued growth, 602 is one of the few urbanized area codes without an overlay, making Phoenix one of the few major cities where seven-digit dialing would still be possible. Under current projections, it will stay that way until at least late 2028. Despite this, ten-digit dialing is required in some portions of the Valley.
