Phone numbers in Monmouth, Illinois
Monmouth has 8 phone prefixes in area code 309.
Biggest holders: Frontier, Verizon Wireless, Mtc Communications. This is the local calling area (rate center) where those prefixes were first assigned.
- Mobile carrier 12%
- Local phone company 25%
- Internet / business phone carrier 38%
- Phone company 25%
Every prefix in Monmouth
Search the first six digits of a number in this list. If it's here, the number started in Monmouth with the carrier shown. If it isn't, check the Illinois page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 309-457 | Frontier | Local phone company | – |
| 309-536 | Verizon Wireless | Mobile carrier | 2003 |
| 309-715 | Mtc Communications | Phone company | 2015 |
| 309-734 | Frontier | Local phone company | – |
| 309-760 | Level 3 (Lumen) | Internet / business phone carrier | 2005 |
| 309-816 | IP Horizon | Internet / business phone carrier | 2020 |
| 309-971 | Nuso | Internet / business phone carrier | 2025 |
| 309-990 | Exiant Communications | Phone company | 2026 |
Most prefixes are pooled: the 10,000 numbers in each are handed out in blocks of 1,000 to different carriers, and people can also take their numbers to another carrier. So the carrier shown is where the prefix started, not a guarantee about any one number. Source: NANPA central office code records, 2026-10-10.