Area Code 231
Michigan
Area code 231 serves Michigan, primarily Muskegon, in the Eastern Time (ET) time zone. It was created from a split of area code 616.
Split Area Code
This area code was created by splitting an existing area code into separate geographic regions. When a split occurs, some customers in the original area code region are assigned the new area code.
This area code was split from area code 616 (Grand Rapids).
In service since: 05-Jun-1999
Demographics & Economics
- Total Population
- 1,173,955
- Population Density
- 62 people/sq mibelow U.S. average (U.S.: 93 people/sq mi)
- Median Household Income
- $63,495below U.S. median (U.S.: $75,144)
- Poverty Rate
- 12.4%near U.S. average (U.S.: 11.5%)
- Unemployment Rate
- 5.3%above U.S. average (U.S.: 3.6%)
- Education Attainment
- Bachelor's Degree+25.9%below U.S. average (U.S.: 33.7%)High School or Lower35.4%
Statistics are population-weighted aggregations from Census ACS 5-year estimates. Population figures are approximate — see Sources & Methodology for details on how area code populations are derived.
See how this area code compares to all US area codes in the Statistics dashboard.
Time Zone
- Eastern Time (ET)
NANPA Relief Status
According to the latest NANPA analysis (July 2026), this area code is not currently listed as exhausting within the next 36 months. No relief planning is in progress for this NPA.
Source: NANPA NPA Relief Planning Reports · See all relief planning statuses
Current Time
Prefix Utilization
Geographic Coverage
State
MI
Major Cities
- Muskegon
- Norton Shores
- Cadillac
- Muskegon Heights
- Big Rapids
- Ludington
- Manistee
- Petoskey
- Wolf Lake
- Cheboygan
- Fremont
- Roosevelt Park
- North Muskegon
- Whitehall
- Canadian Lakes
- Montague
- Shelby
- Newaygo
- Charlevoix
- Kalkaska
- Indian River
- Twin Lake
- Hart
- Kingsley
and 116 more cities
Historical Timeline of Area Code 231
Area code 231 was created on June 5, 1999, through a geographic split of area code 616, one of the original 86 North American area codes assigned in 1999. The split addressed rapid number exhaustion in western Michigan. The parent 616 area code was placed in extraordinary jeopardy on November 29, 1999, less than two months after mandatory dialing commenced. Source: Telecom Michigan.
Key milestones:
- 1947: Original Michigan area codes assigned: 313 (Detroit/eastern), 517 (Lansing/central), 616 (Grand Rapids/western and Upper Peninsula).
- 1961: 906 split from 616 for Michigan's Upper Peninsula (Telecom Michigan).
- June 5, 1999: Area code 231 created by geographic split from 616. Permissive dialing period ran from June 5 through October 2, 1999 (NANPA PL-167).
- October 3, 1999: Mandatory 10-digit dialing began for 231 and remaining 616 territory.
- November 29, 1999: 616 NPA placed in extraordinary jeopardy, less than two months after mandatory dialing commenced (MPSC CC Docket 99-200).
- 2000: Governor John Engler signed MCL 484.2303, granting MPSC authority to implement area code relief. Permissive dialing to wireless numbers ended October 2, 2000.
- July 13, 2002: 269 split from 616 for southwestern Michigan, providing further relief to the parent code.
- 2021: Nationwide transition to mandatory 10-digit dialing for the 988 Suicide and Crisis Lifeline.
- 2035: NANPA projects 231 inventory exhaustion in Q2 2035, triggering relief planning by the Michigan Public Service Commission.
The rapid succession of splits from 616, creating 231 in 1999 and 269 in 2002, reflects the intense numbering pressure on Michigan's western region during the late 1990s wireless growth period.
Regulatory History
Area code 231 has been shaped by several key regulatory actions involving the Michigan Public Service Commission and the FCC. The regulatory framework includes NANPA planning letters, state legislative authority, and FCC delegated authority for number conservation. Source: MPSC CC Docket 99-200
| Year | Event | Docket | Regulatory Action & Impact |
|---|---|---|---|
| 1999 | NPA Split Authorization | NANPA PL-167 | NANPA Planning Letter authorizing the geographic split of 616 NPA, creating the 231 NPA effective June 5, 1999. Permissive dialing ran June 5 through October 2, 1999. (NANPA) |
| 2000 | State Legislative Authority | MCL 484.2303 | Governor Engler signed legislation granting MPSC authority to implement area code relief without prior FCC order, empowering proactive state-level management. (Telecom Michigan) |
| 2001 | Delegated Authority Petition | CC Docket No. 99-200 | MPSC petitioned for delegated authority for number conservation measures including thousands-block number pooling in the Grand Rapids MSA. (MPSC Petition) |
| 2001 | FCC Ex Parte Presentation | CC Docket No. 99-200 | MPSC documented that the 231 NPA is neither in jeopardy nor in need of relief, with 450 central office codes available as of May 2001. (MPSC Ex Parte) |
| 2001 | MPSC Order Confirmation | MPSC Docket U-12850 | MPSC Order documented the Industry Committee's modification of 616 NPA by geographic split to create 231. Confirmed 450 CO codes available. Relief planning deferred. (MPSC Order) |
County Coverage
Population-weighted county share based on aggregated ZCTA population (100% = total mapped population for area code 231).
| County | Population | Share |
|---|---|---|
| Muskegon, MI | 195,297 | 16.6% |
| Newaygo, MI | 118,892 | 10.1% |
| Grand Traverse, MI | 111,626 | 9.5% |
| Antrim, MI | 60,221 | 5.1% |
| Wexford, MI | 58,423 | 5.0% |
| Mecosta, MI | 56,939 | 4.9% |
| Oceana, MI | 51,493 | 4.4% |
| Cheboygan, MI | 50,700 | 4.3% |
| Lake, MI | 49,057 | 4.2% |
| Missaukee, MI | 48,645 | 4.1% |
| Charlevoix, MI | 48,434 | 4.1% |
| Mason, MI | 47,784 | 4.1% |
| Benzie, MI | 46,579 | 4.0% |
| Leelanau, MI | 39,570 | 3.4% |
| Emmet, MI | 38,156 | 3.3% |
| Manistee, MI | 35,167 | 3.0% |
| Kalkaska, MI | 32,969 | 2.8% |
| Osceola, MI | 28,425 | 2.4% |
| Montcalm, MI | 28,009 | 2.4% |
| Ottawa, MI | 12,737 | 1.1% |
| Kent, MI | 8,708 | 0.7% |
| Clare, MI | 4,022 | 0.3% |
| Otsego, MI | 2,058 | 0.2% |
| Mackinac, MI | 44 | 0.0% |
Area Code 231 Family Tree
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Area code 231 was originally assigned in 05-Jun-1999 to serve MI.
Call Context
This area code spans a mix of urban centers and rural communities across MI, with Muskegon as a primary city.
Nearby Area Codes
Area codes geographically closest to 231.
Other Area Codes in Michigan
Area codes that also serve Michigan, linked for easy comparison.