Area code 857

Area codes 617 and 857 are the North American area codes serving Boston and several surrounding communities in Massachusetts—such as Brookline, Cambridge, Newton and Quincy (LATA code 128).

The main area code, 617, was one of the original area codes from October 1947, and originally covered the eastern two-thirds of Massachusetts, from roughly the western end of Worcester County to Cape Cod and the South Coast.

In July 1988, most of the western and southern portions of the old 617 territory, including Worcester, the South Coast and the Cape and Islands was split off as area code 508. It was split again in 1997, when most of Boston's outer suburbs split off as 781. This reduced 617 to Boston itself and its closer-in suburbs—an area largely coextensive with the inner ring of Greater Boston.

This was intended as a long-term solution, but within three years 617 was close to exhaustion once again due to the demand for more phone lines for auxiliary devices (mobile phones, fax machines, pagers, and BBS lines). The supply of numbers was further limited because the entire eastern half of Massachusetts is still a single LATA, and several numbers in 508 were not available for use. On May 2, 2001, 857 was overlaid onto 617. Since then, 10 digit local dialing is mandatory.

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