Phone numbers in Eureka, Illinois
Eureka has 3 phone prefixes in area code 309.
Biggest holders: Frontier, Onvoy. This is the local calling area (rate center) where those prefixes were first assigned.
- Local phone company 67%
- Internet / business phone carrier 33%
Every prefix in Eureka
Search the first six digits of a number in this list. If it's here, the number started in Eureka with the carrier shown. If it isn't, check the Illinois page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 309-304 | Frontier | Local phone company | 2004 |
| 309-466 | Onvoy | Internet / business phone carrier | 2002 |
| 309-467 | Frontier | Local phone company | – |
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.