Area Code Atlas

Establishment of area code 413

In 1947, area code 413 was established as part of the original North American Numbering Plan. It was assigned to the western third of Massachusetts, while area code 617 was assigned to the eastern two-thirds. The dividing line ran through far western Worcester County.

NPA 617 created as an original area code

Area code 617 was created in October 1947 as one of the original North American area codes. It initially served the eastern two-thirds of Massachusetts, including Boston and surrounding communities, as part of the first nationwide telephone numbering plan.

NANP - SPLIT OF THE 617 NUMBERING PLAN AREA

NPA 508 split from 617

In July 1988, area code 508 was created in a split from area code 617. This change divided eastern Massachusetts, with 508 serving central and southeastern regions while 617 continued to serve the Boston area and nearby communities.

NPA 617 split to create 508

Area code 617 was reduced in size on July 16, 1988, when area code 508 was created to serve the surrounding regions. The new code took over most of the western, northern, and southern portions of the original 617 area, including Worcester County, the Merrimack Valley, the South Coast, and Cape Cod and the Islands. 617 continued to serve the Boston metropolitan area.

Permissive dialing begins for 617 and 508

Permissive dialing between area codes 617 and 508 began on July 16, 1988, allowing calls to be completed using either code during the transition period following the split.

Mandatory dialing for 617 and 508 after split

Permissive dialing between area codes 617 and 508 ended on January 1, 1989, requiring callers to use the correct area code for calls within eastern Massachusetts.

Extraordinary NPA-Specific Conservation Procedures for 508 and 617 NPAs (Massachusetts)

NANP-Split of 617 (Massachusetts) Numbering Plan Area (NPA)

NPA 781 split from 617

Area code 781 was split from 617 on September 1, 1997. This split removed the northern, western, and southern portions of the 617 area, creating a code that almost completely surrounds 617 and covers the Boston suburbs. The split was implemented to provide additional numbering resources for the growing metropolitan area, taking over the northern, western, and southern suburbs of Boston and leaving 617 largely coextensive with the inner ring of Greater Boston.

Extension in the Permissive Dialing Period for the 508 and 617 NPA Relief Plans (Massachusetts)

Additional Changes to the Split of 508 & 617 NPAs (Massachusetts)

Extraordinary Jeopardy Procedures for 508, 617, 781 and 978 Numbering Plan Area (NPA) in Massachusetts

NPA 857 overlay introduced on 617

Area code 857 was overlaid onto 617 on May 2, 2001, to address number exhaustion in the Boston area. The overlay required mandatory 10-digit local dialing for all calls within the region. Since then, 10-digit dialing has been mandatory in the 617/857 area.

617/857 NPA projected exhaust by 2059

As of October 2025, the 617/857 overlay complex is projected to be exhausted by the year 2059, according to NANPA exhaust analysis.

617/857 NPA projected exhaust by 2059

The 617/857 overlay complex is projected to exhaust its available numbering resources by the year 2059, according to the October 2025 NPA Exhaust Analysis.