Massachusetts was the only New England state divided into multiple numbering plan areas (NPAs) when the American Telephone and Telegraph Company (AT&T) devised the first nationwide telephone numbering plan in 1947. Area code 617 was assigned to the more populous eastern portion, stretching from roughly the western end of Worcester County to Cape Cod and the South Coast. The rest of the state, roughly everything from Hardwick westward, was served by area code 413.
In July 1988, most of the western, northern, and southern portions of the old 617 territory, including Worcester County, the Merrimack Valley, the South Coast, and the Cape and Islands, were split off as area code 508. Permissive dialing of 617 continued across eastern Massachusetts until January 1, 1989.
In 1997, the northern, western and southern portions of the new 617 split off as 781, which almost completely surrounds 617. This made 617 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). On May 2, 2001, 857 was overlaid onto 617. Since then, 10-digit local dialing has been mandatory.
Some mobile telephone numbers from the 1990s assigned to communities in the area surrounding 617 (which is now the 781 area code) kept the 617 area code after the split.
Area code 508 was split from 617 on July 16, 1988. Area code 978 subsequently split from 508 on September 1, 1997.
Area code 781 was split from 617 on September 1, 1997.
As of 2018, the 617/857 NPA is projected to be exhausted by 2041.1
The numbering plan area 617/857 includes portions of the following counties:
This includes the following communities:
The NPA includes central offices with the following prefix format 617-NXX:234
The NPA includes central offices with the following prefix format 857-NXX:
Main article: N11 code
2018 October NANPA Exhaust Projections https://www.nationalnanpa.com/reports/2018-2_NPA_Exhaust_Projections_Final.pdf ↩
Staff writer (2023). "Area Code 617/857 map and data profile". Zipdatamaps. Retrieved January 12, 2023. https://www.zipdatamaps.com/area-code-617 ↩
Staff writer (2016). "Central Office Code information". Directory-Assistance.net. Archived from the original on June 30, 2011. Retrieved January 12, 2023. https://web.archive.org/web/20110630192051/http://www.directory-assistance.net/npanxx/617.html ↩
Staff writer (2009). "617 Area Code exchanges". areacodedownload.com. Archived from the original on February 8, 2009. Retrieved January 12, 2023. https://web.archive.org/web/20090208005833/http://www.areacodedownload.com/617/index.html ↩
Operational Services Brief: 311 in Massachusetts, Edward J. Collins Center for Public Management Publications, 10-24-2008 https://scholarworks.umb.edu/cpm_pubs/10/ ↩
511 Massachusetts http://www.mass.gov/511 ↩
Mass Relay http://www.mass.gov/massrelay/ ↩
Dig Safe http://www.call811.com/ ↩
FCC Doc. No. 92-105 https://fjallfoss.fcc.gov/edocs_public/attachmatch/DOC-257293A1.doc ↩