770 is a telephonearea code in the NANP, assigned to metropolitan Atlanta, Georgia's suburbs and exurbs. It was split from 404 in 1995, just three years after the 706 split. Due to exurban resident complaints about the original BellSouth maps leaving them no longer associated with the well-known 404, those rapidly-growing areas were put back into 404, forcing the entire suburban ring of metro Atlanta to lose 404 much earlier than necessary.
Today, 770 is reserved for use outside roughly Interstate 285, with 404 reserved for inside the Perimeter (I-285). Both codes are now overlaid by 678, and 470 (potentially very confusing with 404 and 770, and adjacent 478).
Currently, cell phone subscribers in the region can choose from either the 404, 678, or 770 area code when signing up for service. When the area was originally divided in 1995, all cellphones stayed with 404, which balanced the fact that most of the landline area went to 770.
In shorthand, 770 is sometimes written by local residents as 7/phone-number, 7-phone-number or 7)phone-number
Atlanta, Georgia, was the first city in the United States to have mandatory 10-digit dialing throughout its metro area, roughly coinciding with the 1996 Summer Olympics in Atlanta. Atlanta was used as the test case not only due to its size, but also because it enjoyed the world's largest fiber optic bundle at the time (five times that of New York at the time), and it was home to BellSouth (now part of AT&T), then the Southeastern Regional Bell Operating Company.
