307 area code
Where the 307 area code is, its overlay and how to dial a +1 307 number from anywhere.
The 307 area code is in Casper, Wyoming, United States (Mountain (MT)). To call from abroad: +1 307 555-0123.
The 307 area code is a geographic North American Numbering Plan (NANP) code covering Casper, Wyoming. It has been in service since 01-Jan-1947 and sits in the Mountain (MT) time zone.
How to dial a 307 number
+1 307 555-01231 307 555-0123Cities in the 307 area code
A 307 number is usually in one of these places in Wyoming — 4 counties.
Frequently asked questions
Where is the 307 area code?
The 307 area code is in Casper, Wyoming, United States (Mountain (MT)).
Do I have to dial 10 digits for 307?
Local calls within 307 may use seven digits; ten-digit dialling always works.
How do I call a 307 number from another country?
Dial your exit code (or +), then 1, then 307, then the number: +1 307 555-0123.
Source: NANPA numbering plan. An area code covers a region, not a precise address — a 307 number does not pinpoint a street or ZIP code.
Number holders in area code 307
Each prefix (the three digits after the area code) is assigned by NANPA to one telephone company. 525 prefixes are in use in 307, shared by 55 companies. The largest holders:
| Company | Prefixes | Share |
|---|---|---|
| Qwest Corporation | 83 | 16% |
| Union Telephone Company | 65 | 12% |
| Cellco Partnership Dba Verizon Wireless | 60 | 11% |
| New Cingular Wireless PCS, LLC | 49 | 9% |
| Onvoy, LLC | 40 | 8% |
| Level 3 Communications, LLC | 27 | 5% |
Source: NANPA central office code assignments. A number keeps its original prefix when it is ported to another carrier.
Complaints about 307 numbers
- Reports to the FTC, last 30 days
- 392
- Recorded messages or robocalls
- 63%
- Rank among area codes
- #250 of 670
- Most reported subjects
- Other (151)
- Reducing your debt (credit cards, mortgage, student loans) (137)
- Calls pretending to be government, businesses, or family and friends (20)
Period Aug 26 – Sep 24, 2026. These are the numbers shown on the caller ID of the reported calls; many are spoofed and do not belong to the real caller.
Source: US Federal Trade Commission, Do Not Call reported calls data (daily files).
All US area codes United States +1 Map of area code 307 — cities & rate centres