Area Code 351 — Boston, Massachusetts

NANP area code

351

UTC−5, UTC−4 during daylight saving

State
Massachusetts
Primary city
Boston
Time zone
Eastern
In service
2001
Overlay
978

The code reaches 101 communities and 5 counties across Massachusetts.

Was this call legitimate?

The area code itself carries no risk signal. 351 is assigned to Boston, Massachusetts, so a call from it is consistent with a real caller in that area — but the digits alone prove nothing, because they can be forged.

Caller ID is set by whoever places the call, not verified by the network. That is why neighbour spoofing works: an operation anywhere in the world can display a number that matches the area code — and often the first three digits after it — of the person being called, so the call looks local. Every community in the 351 territory is a plausible-looking origin for a forged 351 number, which is why one can be made to look like a neighbour to so many people. The same applies to its overlay code 978, which serves the same ground.

If you did not recognise the call: let it go to voicemail — a legitimate caller with real business will leave one. Do not return the call using the number shown; look the organisation up independently and call the number you found. Never confirm personal details, card numbers, or one-time codes to someone who called you, however plausible the number looked.

Codes.zone publishes no complaint counts, risk scores, or caller identities. We hold no data on individual numbers and will not estimate what we cannot source.

Local time and when to call back

Time there now

Eastern · UTC−5, UTC−4 during daylight saving

Reasonable callback window

8:00 AM – 9:00 PM

local time in Eastern

Federal rules bar telemarketing calls to a residence outside 8:00 AM–9:00 PM in the called party's own time zone. It is a sensible bound for a personal callback too — and a caller who rang you well outside it was not observing it.

Overlay codes and ten-digit dialling

351 does not have its territory to itself. 978 covers the same ground, serving Boston and the rest of the 351 territory. An overlay is what a regulator adds when a region runs out of assignable numbers: rather than splitting the area and forcing half the residents to change their number, a second code is laid over the top and new numbers are issued from it.

The practical consequence: two neighbours on the same street can hold numbers in different area codes, so the code tells you nothing about which part of town a caller is in — and local calls must be dialled as all ten digits, because seven is no longer unambiguous.

Cities served

largest 20 by ZIP count
Communities served by area code 351, ranked by how many ZIP codes each holds.
CityZIP codesCounty
Boston36Middlesex County
Worcester15Worcester County
Cambridge6Middlesex County
Andover5Essex County
Lowell5Middlesex County
Haverhill4Essex County
Lawrence4Essex County
Groton3Middlesex County
North Reading3Middlesex County
Acton2Middlesex County
Billerica2Middlesex County
Gloucester2Essex County
Medford2Middlesex County
Peabody2Essex County
Salem2Essex County
Westminster2Worcester County
Amesbury1Essex County
Ashburnham1Worcester County
Ashby1Middlesex County
Athol1Worcester County

81 further communities not listed. All Massachusetts area codes →

Each point is a community served by 351, plotted from its record coordinates. The outline is the convex envelope of those points — a footprint, not a boundary.
  • Reference points and footprint
  • Not an official NANPA boundary
  • Not a USPS delivery area

Scope every community matched to 351. Source geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot), GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated . Coordinates are place reference points, not boundaries.

Counties

Prefixes inside 351

We do not publish the NXX prefixes inside 351. The assignment of prefixes to rate centres comes from LERG routing data, which is proprietary, and we will not estimate it from postal data — ZIP codes and telephone prefixes do not map onto each other. Awaiting a clean-rights NPA-NXX source.

Why this code exists

351 is the newer code here, added in 2001 over 978 (1997). The older code had run out of exchanges to assign, and an overlay avoids the alternative — splitting the region and forcing half its residents to renumber. New lines have been issued from 351 since.