Area Code 231

About Area Code 231

Area code 231 is a geographic telephone area code assigned to Traverse City, Michigan. It operates in the Eastern time zone and was first introduced in 1999. Split from 616. Northwestern Michigan.

Within Michigan, area code 231 shares numbering capacity with 11 other area codes. The state's 10,050,511-person population (2023 Census Bureau estimate) is served by a combined 12 active codes, with 231 primarily responsible for the Traverse City region. Michigan's state capital is Lansing, and its largest city is Detroit.

When you receive a call from a 231 number on your Caller ID, the call originated from a phone number assigned to the 231 area code — but be aware that Local Number Portability (in effect since 2003) means the caller could be physically located anywhere in the US or Canada. Area code 231 only confirms where the number was originally assigned.

Where is the 231 area code located?

Area code 231 is assigned to Traverse City, Michigan, in the Eastern time zone. The state of Michigan uses 12 active area codes, and 231 is one of them. Calls placed from the 231 area code originate from numbers assigned by NANPA — the North American Numbering Plan Administrator — and the 231 prefix appears on Caller ID for both landline and wireless calls placed from this region.

The Eastern time zone observes Daylight Saving Time, shifting from UTC-5 to UTC-4 in summer. The local time shown above is always current, so you can quickly check whether it's a reasonable hour to call back.

What cities and counties use the 231 area code?

The 231 area code serves 8 notable cities, listed below in order of population. The largest city in the 231 territory is Detroit (620,376 residents in Wayne County).

• Detroit, MI — 620,376 residents (40.9% of 231 numbers)
• Grand Rapids, MI — 198,917 residents (13.1% of 231 numbers)
• Warren, MI — 138,816 residents (9.1% of 231 numbers)
• Sterling Heights, MI — 133,896 residents (8.8% of 231 numbers)
• Ann Arbor, MI — 123,854 residents (8.2% of 231 numbers)
• Lansing, MI — 112,744 residents (7.4% of 231 numbers)
• Flint, MI — 79,948 residents (5.3% of 231 numbers)
• Dearborn, MI — 109,976 residents (7.2% of 231 numbers)

Phone number format in area code 231

All phone numbers within area code 231 follow the standard North American 10-digit format:(231) NXX-XXXX. The NXX is the central office prefix (also called an "exchange") and XXXX is the subscriber line number. For long-distance calls within the NANP, dial 1 + 231 + NXX + XXXX. From outside North America, dial your country's international access code, then 1 (the NANP country code), then the 10-digit number.

If you need to verify whether a specific 231 number is wireless, landline, or VoIP, you can use our reverse phone lookup tool. Be aware that number portability means the area code no longer guarantees the caller's physical location — only where the number was first assigned.

History of area code 231

Split from 616. Northwestern Michigan.

The original 86 area codes were assigned by AT&T and Bell Labs in 1947 as part of the North American Numbering Plan. At the time, rotary-dial phones meant codes with lower digits (like 212 for NYC, 213 for LA, 312 for Chicago) were given to the largest cities because they took less time to dial. Today's area code assignments still reflect those early choices, even though touch-tone and cell phones made the original reason obsolete.

Is the 231 area code safe to answer?

Area code 231 itself is a normal geographic code with no elevated spam risk. That said, scammers can spoof any area code — including 231 — so if you don't recognize the full number, let it go to voicemail and verify the caller's identity before calling back.