Area code 770

Area code 770 is a telephone area code in the North American Numbering Plan (NANP) serving all or part of 29 counties in North Georgia, including most of Atlanta's suburbs. It was split from 404 in December 1995, just three years after the 706 (now overlays with area code 762) split.

The creation of 706 was intended as a long-term solution to relieve exchanges in North Georgia. However, within a short time 404 was close to exhaustion once again due to the proliferation of cell phones, fax machines, and pagers in the fast-growing Atlanta metro area. While it was apparent that the metro area could not stay entirely within 404, 770 was put into service sooner than anticipated as part of the fallout from the creation of 706. When 706 was originally created, it included several fast-growing exurbs of Atlanta. However, BellSouth put them back into 404 after residents complained about no longer being associated with the better-known area code. However, 404 had been close to exhaustion even before the creation of 706, and the restoration of the exurban areas forced the entire suburban ring of metro Atlanta to lose 404 sooner than originally planned.

Currently, 770 completely surrounds 404. The two area codes are split roughly by Interstate 285, known locally as the Perimeter. Generally, 770 includes most of the metro area outside the Perimeter, while 404 serves Atlanta itself and most suburbs inside the Perimeter; a few cities are split between the two codes. Both codes are now overlaid by 678, and 470. The metro Atlanta region (404, 770, 678, 470 and parts of 706 and 256) is a local calling area, and no long-distance charges are applied for calls from one portion of the metro to the other.

...
Wikipedia