Every ZIP code in the United States, with weather, radar, trivia and the numbers behind it. Five digits since 1963!

ZIP stands for Zone Improvement Plan. The codes went live on July 1, 1963.The lowest ZIP code is 00501 — the IRS in Holtsville, New York.The highest ZIP code is 99950, in Ketchikan, Alaska.Type 07734 into a calculator and turn it upside down: hELLO. It is Keansburg, New Jersey.12345 belongs to one company: General Electric in Schenectady, New York.The first digit is a region: 0 is New England and New Jersey, 9 is the West Coast, Alaska and Hawaii.Mr. ZIP, the cartoon mailman, was the mascot that sold the idea to America.ZIP+4 arrived in 1983 and can narrow a ZIP down to one side of one block.A ZIP code is a mail route, not a place: plenty of them cross county and even state lines.Play ZIP Hunt: guess the secret ZIP code of the day in six tries.
zipcodes.pro — AREA-CODE/231

231 area code

Area code 231 is in Michigan. It covers Muskegon, Traverse City, Cadillac and 164 other places: 142 ZIP codes in Muskegon, Grand Traverse, Newaygo and 17 other counties. Local time there is , Eastern Time. In service since 1999, with no overlay.

Time zone
Eastern
Largest city
Muskegon
Overlays
none
In service since
1999
Rate centres
99
Prefixes assigned
572 (5,720,000 numbers)

Who calls from a 231 number

NANPA records the carrier each block of 231 numbers is assigned to. Of the 5.1 million 231 numbers assigned, 49% are with cable, internet-calling, business and other carriers (Onvoy and Interactive Services Network); 24% with local phone companies (AT&T and Frontier); 23% with mobile carriers (AT&T Mobility and Verizon Wireless); 4% with paging companies.

That is who the numbers were assigned to: people keep their number when they change carrier, so any one number may have moved since.

Carriers holding the most 231 numbers
CarrierKindShare
OnvoyCable, VoIP, other16%
AT&TLandline9%
AT&T MobilityMobile9%
Interactive Services NetworkCable, VoIP, other9%
Verizon WirelessMobile8%
FrontierLandline7%

An area code says where a number was issued, not where the caller is: people keep their numbers when they move, and caller ID can be set to show any number, which the FCC calls spoofing. If a call you did not expect asks for money or personal details, the FCC advises hanging up and calling the company back on a number you look up yourself. Unwanted calls can be reported to the FTC at ReportFraud.ftc.gov.

Places in area code 231

The 88 places with a telephone rate centre of their own using 231, largest first. Each links to its ZIP codes.

Places in area code 231
PlaceZIP codesPopulation
Muskegon, MI 6 37,226
Traverse City, MI 4 15,593
Cadillac, MI 1 10,445
Big Rapids, MI 1 8,477
Ludington, MI 1 7,676
Williamsburg, MI 1 6,657
Manistee, MI 1 6,275
Petoskey, MI 1 5,856
Lake, MI 1 5,268
Cheboygan, MI 1 4,820
Fremont, MI 2 4,568
Boyne City, MI 1 3,825
Mc Bain, MI 1 3,801
Holton, MI 1 3,520
Leroy, MI 1 3,383
Whitehall, MI 1 3,024
Shelby, MI 1 2,577
Kalkaska, MI 1 2,539
Reed City, MI 1 2,517
Newaygo, MI 1 2,512
Charlevoix, MI 1 2,392
Elmira, MI 1 2,170
Twin Lake, MI 1 2,036
East Jordan, MI 1 2,023
Hart, MI 1 1,924
Kingsley, MI 1 1,785
Irons, MI 1 1,715
Evart, MI 1 1,667
Howard City, MI 1 1,636
Elk Rapids, MI 1 1,624
Ravenna, MI 1 1,540
Manton, MI 1 1,511
Mancelona, MI 1 1,476
Scottville, MI 1 1,474
White Cloud, MI 1 1,280
Baldwin, MI 1 1,261
Coral, MI 1 1,245
Frankfort, MI 1 1,225
Fruitport, MI 1 1,212
Grant, MI 1 1,096
Harbor Springs, MI 1 1,086
Central Lake, MI 1 1,051
Bellaire, MI 1 1,008
Buckley, MI 1 936
Hesperia, MI 1 934
Pentwater, MI 1 872
Alanson, MI 1 834
Interlochen, MI 1 791
Mackinaw City, MI 1 778
Pellston, MI 1 755
Lake City, MI 1 705
Merritt, MI 1 631
Morley, MI 1 624
Marion, MI 1 581
Suttons Bay, MI 1 555
South Boardman, MI 1 553
Kaleva, MI 1 542
Northport, MI 1 465
Mecosta, MI 1 464
Mesick, MI 1 423
Boyne Falls, MI 1 361
Wellston, MI 1 353
Fife Lake, MI 1 343
Brethren, MI 1 318
Eastport, MI 1 311
Onekama, MI 1 305
Luther, MI 1 303
Walloon Lake, MI 1 294
Alba, MI 1 282
Lake Ann, MI 1 273
St. James, MI — 269
Ellsworth, MI 1 265
Wolverine, MI 1 265
Bear Lake, MI 1 264
Harrietta, MI 1 230
Falmouth, MI 1 222
Beulah, MI 1 218
Fountain, MI 1 204
Tustin, MI 1 203
Brutus, MI 1 198
Honor, MI 1 172
Stanwood, MI 1 162
Chippewa Lake, MI 1 157
Alden, MI 1 133
Lake Leelanau, MI 1 124
Free Soil, MI 1 112
Levering, MI 1 73
Old Mission, MI 1 —

Nearby places using 231

These places have no rate centre of their own in NANPA's records; the nearest one uses 231. Near an area-code boundary that can be wrong for part of a town.

ZIP codes in area code 231

142 ZIP codes in 133 towns, by the town each is mailed to, largest first. Each links to its own page.

Where 231 numbers are issued

NANPA's rate centres with the most 231 prefixes (each prefix is 10,000 numbers), under NANPA's own abbreviated names.

Rate centres using area code 231
Rate centrePlacePrefixes
MUSKEGON Muskegon 68
TRAVERSECY Traverse City 53
PETOSKEY Petoskey 22
CADILLAC Cadillac 21
BIG RAPIDS Big Rapids 19
LUDINGTON Ludington 14

Counties

The counties of its ZIP codes, most residents first, with how many of its ZIP codes each has.

Which code covers where you are now? What area code am I in? answers from your location.

Questions about area code 231

Where is area code 231?

Area code 231 is in Michigan. It covers Muskegon, Traverse City, Cadillac and 164 other places: 142 ZIP codes in Muskegon, Grand Traverse, Newaygo and 17 other counties.

What ZIP codes are in area code 231?

142 ZIP codes, by the town each is mailed to: Muskegon (6, 49440 to 49445), Traverse City (4, 49684 to 49696), Cadillac (49601), Big Rapids (49307) and 129 more towns. The full list is on this page.

What time zone is area code 231 in?

Eastern time.

Is a 231 number a mobile or a landline?

It can be either. 23% of 231 numbers are assigned to mobile carriers and 24% to local phone companies (NANPA, 2026-10-10); the rest are with cable, internet-calling, business and paging carriers. A number keeps its area code when it moves to another carrier.

Does a 231 number mean the caller is in Michigan?

Not necessarily. An area code says where the number was first issued. People keep their numbers when they move or switch carriers, and calling software can show any number, so a 231 call can come from anywhere.

Other area codes in Michigan

All 13 Michigan area codes, by area, with the cities each covers

Source: NANPA NPA database, central office code and thousands-block assignments, 2026-10-10. Places are matched to NANPA's rate centres by name; see sources.

Cite this page

zipcodes.pro. “Area code 231.” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/area-code/231

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