When the American Telephone and Telegraph Company (AT&T) published the first nationwide telephone numbering plan for Operator Toll Dialing in 1947, Massachusetts was divided into two numbering plan areas (NPAs), the only state in New England to be split between multiple NPAs. The western part of the state received area code 413, while the eastern two-thirds (including Boston and Worcester) were assigned 617. The dividing line between the two NPAs ran through far western Worcester County. Everything west of the tributary exchange areas of the control switching points in Orange, Petersham, Barre, Oakham, North Brookfield, Sturbridge and Southbridge comprised the 413 NPA, so that the border between the two NPAs was formed by the eastern borders of the 413 exchange areas of Northfield, Millers Falls, Montague, Amherst, Gilbertville, Belchertown, Ware, Warren and Brimfield.[1]
As western Massachusetts is not as densely populated as the eastern portion, 413 remained the region's sole area code even as the eastern portion of the state went from one area code to four from 1988 to 1997 (since augmented by an additional four overlays). As a result, 413 is also one of the few original area codes (not counting those that cover an entire state) that have not been split or overlaid.
