NANP area code
351
UTC−5, UTC−4 during daylight saving
- State
- Massachusetts
- Primary city
- Boston
- Time zone
- Eastern
- In service
- 2001
- Overlay
- 978
NANP area code
351
UTC−5, UTC−4 during daylight saving
The code reaches 101 communities and 5 counties across Massachusetts.
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.
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.
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.
| City | ZIP codes | County |
|---|---|---|
| Boston | 36 | Middlesex County |
| Worcester | 15 | Worcester County |
| Cambridge | 6 | Middlesex County |
| Andover | 5 | Essex County |
| Lowell | 5 | Middlesex County |
| Haverhill | 4 | Essex County |
| Lawrence | 4 | Essex County |
| Groton | 3 | Middlesex County |
| North Reading | 3 | Middlesex County |
| Acton | 2 | Middlesex County |
| Billerica | 2 | Middlesex County |
| Gloucester | 2 | Essex County |
| Medford | 2 | Middlesex County |
| Peabody | 2 | Essex County |
| Salem | 2 | Essex County |
| Westminster | 2 | Worcester County |
| Amesbury | 1 | Essex County |
| Ashburnham | 1 | Worcester County |
| Ashby | 1 | Middlesex County |
| Athol | 1 | Worcester County |
81 further communities not listed. All Massachusetts area codes →
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.
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.
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.