Area code 231: where it is and who calls from it
Area code 231 is in Michigan.
Northwestern Michigan (Muskegon, Traverse City, Ludington, Petoskey)
| Where | Michigan |
|---|---|
| Time zone | Eastern Time ยท local time |
| In service since | 1999 |
| Overlay | No |
| Prefixes assigned | 572 of 792 possible (72%) |
Where 231 numbers started
Every prefix is assigned to a rate center, the local calling area it was set up in. These are the biggest in 231, with how many prefixes each has.
Plus 39 smaller rate centers.
Who holds 231 numbers
- Mobile carrier 26%
- Local phone company 26%
- Internet / business phone carrier 33%
- Paging service 4%
- Phone company 11%
| Carrier | Type | Prefixes | Share |
|---|---|---|---|
| AT&T (local phone) | Local phone company | 73 | 13% |
| AT&T Mobility | Mobile carrier | 72 | 13% |
| Onvoy | Internet / business phone carrier | 53 | 9% |
| Frontier | Local phone company | 52 | 9% |
| Interactive Services Network | Internet / business phone carrier | 43 | 8% |
| Verizon Wireless | Mobile carrier | 42 | 7% |
| 123.NET | Phone company | 34 | 6% |
| T-Mobile (including Sprint) | Mobile carrier | 28 | 5% |
| Charter / Spectrum | Internet / business phone carrier | 20 | 3% |
| Level 3 (Lumen) | Internet / business phone carrier | 19 | 3% |
Most prefixes are pooled: the 10,000 numbers in each are handed out in blocks of 1,000 to different carriers, and people can also take their numbers to another carrier. So the carrier shown is where the prefix started, not a guarantee about any one number.
States served: Michigan.
Other area codes in Michigan
248 269 313 517 586 616 679 734 810 906 947 989
Got a call from 231?
An area code tells you where a number was first assigned, not where the caller is. People keep their numbers when they move, and scammers can fake any number. If you weren't expecting the call, let it go to voicemail.
If the call shows a 231 number that matches the first six digits of your own, that's often neighbor spoofing. Use the box above to check the full number.
Area code facts from the NANPA area code database (updated 10/06/2026); prefixes and carriers from NANPA's central office code records (updated 2026-10-10). Place description adapted from Wikipedia, CC BY-SA 4.0.