Area Code 231 — Muskegon, Michigan

NANP area code

231

UTC−5, UTC−4 during daylight saving

State
Michigan
Primary city
Muskegon
Time zone
Eastern
In service
1999

The code reaches 141 communities and 22 counties across Michigan.

Was this call legitimate?

The area code itself carries no risk signal. 231 is assigned to Muskegon, Michigan, 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 231 territory is a plausible-looking origin for a forged 231 number, which is why one can be made to look like a neighbour to so many people.

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

231 is the only area code serving its territory — it has no overlay in the current numbering plan for Michigan. Where a region has no overlay, a number's area code still corresponds to a single geographic area.

Cities served

largest 20 by ZIP count
Communities served by area code 231, ranked by how many ZIP codes each holds.
CityZIP codesCounty
Muskegon6Muskegon County
Traverse City4Grand Traverse County
Fremont2Newaygo County
Gaylord2Otsego County
Acme1Grand Traverse County
Afton1Cheboygan County
Alanson1Emmet County
Alba1Antrim County
Alden1Antrim County
Arcadia1Manistee County
Bailey1Muskegon County
Baldwin1Lake County
Bay Shore1Charlevoix County
Bear Lake1Manistee County
Beaver Island1Charlevoix County
Bellaire1Antrim County
Benzonia1Benzie County
Beulah1Benzie County
Big Rapids1Mecosta County
Bitely1Newaygo County

121 further communities not listed. All Michigan area codes →

Each point is a community served by 231, 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 231. 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 231

We do not publish the NXX prefixes inside 231. 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.