Phone numbers in Eldorado, Illinois
Eldorado has 3 phone prefixes in area code 618.
Biggest holders: Frontier, Mcc Network Services, Onvoy. This is the local calling area (rate center) where those prefixes were first assigned.
- Local phone company 33%
- Internet / business phone carrier 33%
- Phone company 33%
Every prefix in Eldorado
Search the first six digits of a number in this list. If it's here, the number started in Eldorado with the carrier shown. If it isn't, check the Illinois page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 618-273 | Frontier | Local phone company | – |
| 618-297 | Mcc Network Services | Phone company | – |
| 618-591 | Onvoy | Internet / business phone carrier | 2020 |
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.