Area Code 406

About Area Code 406

Area code 406 is a geographic telephone area code assigned to Billings, Montana. It operates in the Mountain time zone and was first introduced in 1947. Original NANP code. State-wide Montana.

Within Montana, area code 406 is the only active area code, covering the entire state. The state's 1,122,864-person population (2023 Census Bureau estimate) is served by a combined 1 active code, with 406 primarily responsible for the Billings region. Montana's state capital is Helena, and its largest city is Billings.

When you receive a call from a 406 number on your Caller ID, the call originated from a phone number assigned to the 406 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 406 only confirms where the number was originally assigned.

Where is the 406 area code located?

Area code 406 is assigned to Billings, Montana, in the Mountain time zone. The state of Montana uses 1 active area code, and 406 is the only one. Calls placed from the 406 area code originate from numbers assigned by NANPA — the North American Numbering Plan Administrator — and the 406 prefix appears on Caller ID for both landline and wireless calls placed from this region.

The Mountain time zone observes Daylight Saving Time, shifting from UTC-7 to UTC-6 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 406 area code?

The 406 area code serves 15 notable cities, listed below in order of population. The largest city in the 406 territory is Billings (117,435 residents in Yellowstone County).

• Billings, MT — 117,435 residents (25.6% of 406 numbers)
• Missoula, MT — 75,091 residents (16.3% of 406 numbers)
• Great Falls, MT — 60,442 residents (13.2% of 406 numbers)
• Bozeman, MT — 53,298 residents (11.6% of 406 numbers)
• Butte, MT — 34,494 residents (7.5% of 406 numbers)
• Helena, MT — 33,469 residents (7.3% of 406 numbers)
• Kalispell, MT — 25,864 residents (5.6% of 406 numbers)
• Havre, MT — 9,469 residents (2.1% of 406 numbers)
• Anaconda, MT — 9,213 residents (2% of 406 numbers)
• Miles City, MT — 8,341 residents (1.8% of 406 numbers)

Phone number format in area code 406

All phone numbers within area code 406 follow the standard North American 10-digit format:(406) 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 + 406 + 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 406 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 406

Original NANP code. State-wide Montana.

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 406 area code safe to answer?

Area code 406 itself is a normal geographic code with no elevated spam risk. That said, scammers can spoof any area code — including 406 — so if you don't recognize the full number, let it go to voicemail and verify the caller's identity before calling back.