The following chart shows the original 86 Numbering Plan Areas (NPAs, or area codes) assigned in 1947. You can also see the map at map1947.html. Note that in several cases, the boundaries have since been realigned, so that, while many of the area codes are familiar, there are a few surprises. Entries shown in green have not changed (or changed only minutely) in the half century the NANP has existed. The second chart illustrates certain patterns in the initial assignments. A separate page details the evolution from the original area codes to the present day.

A simple pattern unified the original assignments of area codes in 1947. First, any state or province that had only a single area code (or shared an area code with an adjacent province) was assigned an area code with a 0 as the middle digit. All area codes in multi-code states and provinces were assigned with 1 as the middle digit. Since telephones in that day were rotary dial, consideration was also given to the number of “dial pulls” required for each area code; area codes with a small number of dial pulls were assigned to the largest cities and states. Thus, New York City, Los Angeles, and Chicago got 212, 213, and 312, while New Jersey, Washington DC, Maryland, and Connecticut got 201, 202, 301, and 203. There were some odd exceptions, though: Dallas, western Massachusetts, and Manitoba were all promoted above their importance in 1947, while Boston, Kansas City (both Kansas and Missouri), and the suburbs of New York City were demoted.

Note the clear diagonal patterns in both sets of assignments.

✻ Area code 902 was originally assigned to New Brunswick, Nova Scotia, and Prince Edward Island, plus what was at the time the U.K. dominion of Newfoundland (now the Canadian province of Newfoundland and Labrador).