It was back in 1947 when the North American Numbering plan (NANP) went into effect. Each telephone is assigned a seven-digit telephone number unique only within its respective plan area. The telephone number consists of a three-digit central office code and a four-digit station number. The combination of an area code and the telephone number serves
as a destination routing address in the public switched telephone network. In November of 1951 NANP was implemented by AT&T and Georgia had the area code of 404. My home phone was 404-475-7411 but we never dialed the area code to call any other 404 number. you didn’t even have to dial the whole number, if you were calling me you just had to dial 5-7411. In July of 1954 they split the Georgia area code into two, 404 for the north and 912 for the southern part. In May of 1992 they split 404 into two again,
404 serving the Atlanta area and 706 for the rest of the northern state. I believe this is when we had to start dialing the whole number, like 404-475-7411. In August of 1995 , just three years later, 404 is split again. 404 is now for inside the I-285 perimeter and 770 is added to serve the outskirts of Atlanta.
My phone number changed to 770-475-7411. I also got another phone line to support my modem and that number was 770-664-6250. Three more years passed and then in January of 1998 the boundaries of the 404/770 were erased and 678 area code was added. Things were changing, rapidly adding people, modems and now cell phones caused these fluctuations. In August of 2000 912 was split into thirds, 229 serving southwestern Georgia, 912 for Southeastern Georgia and 478 serving 19 counties in central Georgia. In September of 2001 470 was added to the 404/678 metro Atlanta area codes. In September 2005 they overlaid 762 with area code 706. When I got my cell phone I was given a choice of 404, 770 or 678 and I chose the latter, just to be different.