North American Numbers Source-cited · ownership disclosed
Area code
231
In service
United States · since 1999

Traverse City / Muskegon

Northwestern Lower Peninsula of Michigan, created by a 1999 split of area code 616; covers the northern West Michigan coast and much of Northern Michigan.

The essentials Numbering data · NumberResearch · as of 2026-09-18
Place
Traverse City / Muskegon
Type
geographic
Status
in service
In service since
1999
Projected exhaust
2068 Q1

Status, dates and counts are read from NumberResearch (NANPA / CNAC / FCC records). Assignment records show initial assignees, not the carrier serving a number today.

A · Where it is

Where 231 is

Northwestern Lower Peninsula, roughly from a Mackinac Bridge-aligned line westward to Lake Michigan..

Communities served wholly or partly by 231:

Traverse CityMuskegonCadillacPetoskeyCheboyganLudingtonBig Rapids

Also serves Bois Blanc Township in the Straits (normally 906 territory) due to ferry ties.

B · Relationships

How it relates to other codes

The codes 231 was split from, spawned, or shares its area with. A split divides the map and changes some numbers; an overlay shares the same ground and changes none — what's the difference?

Split from · 1999 616 Grand Rapids Split from 616.
Related 906 Upper Peninsula Upper Peninsula to the north.
Related 989 Saginaw / Bay City / Midland Adjacent to the east.
What's changing. No overlay; single code.
C · History

How 231 got here

1999-06
Established through a split of area code 616 (NANPA Planning Letter 167); serves Traverse City, Muskegon, Cadillac and the northwestern Lower Peninsula.
Source: Wikipedia
D · Capacity

How full it is

Prefixes assigned
596
Prefixes available
204
Thousands-blocks assigned
2,430

Prefix-assignment counts describe allocation to carriers, not how many individual numbers are in use. Full technical records: NumberResearch ↗.

Compare 231 with another code →
Sources
Wikipedia ↗
Area code 231
NumberResearch.org ↗
Live status, dates, assignment counts and exhaust forecast — data as of 2026-09-18 (CC BY 4.0).

Place, relationships and history above are compiled by North American Numbers from the sources listed and last checked 2026-09-18. A check date is not an expert review — see how this is made. Flag an error.