Editing Seven-digit dialing (section)

===1951 to 1960===
Direct Distance Dialing (DDD) trials were conducted by the end of 1951, in which subscribers in Englewood, New Jersey, could dial long-distance calls to a select group of remote destinations, as far away as San Francisco, by using an area code.

DDD technology expanded to other major cities, By 1960, it was available in a few places in Canada, as well as most large American cities. This decade is notable for implementation of some thirty more area codes, including in Alaska, Hawaii, and the Caribbean.