Phone numbers in Crystal Lake, Illinois
Crystal Lake has 21 phone prefixes in area codes 779, 815.
Biggest holders: AT&T (local phone), Onvoy, MetroPCS (T-Mobile). This is the local calling area (rate center) where those prefixes were first assigned.
- Mobile carrier 10%
- Local phone company 33%
- Internet / business phone carrier 52%
- Paging service 5%
Every prefix in Crystal Lake
Search the first six digits of a number in this list. If it's here, the number started in Crystal Lake with the carrier shown. If it isn't, check the Illinois page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 779-220 | Bandwidth | Internet / business phone carrier | 2011 |
| 779-356 | Fractel | Internet / business phone carrier | 2020 |
| 779-388 | Onvoy | Internet / business phone carrier | 2024 |
| 779-800 | Onvoy | Internet / business phone carrier | 2013 |
| 779-994 | Peerless Network Of Illinois | Internet / business phone carrier | 2013 |
| 815-204 | Spok | Paging service | – |
| 815-219 | MetroPCS (T-Mobile) | Mobile carrier | 2006 |
| 815-261 | MCImetro (Verizon Business) | Internet / business phone carrier | – |
| 815-276 | Teleport Communications America | Internet / business phone carrier | – |
| 815-301 | Level 3 (Lumen) | Internet / business phone carrier | – |
| 815-356 | AT&T (local phone) | Local phone company | – |
| 815-404 | MetroPCS (T-Mobile) | Mobile carrier | – |
| 815-425 | Level 3 (Lumen) | Internet / business phone carrier | – |
| 815-444 | AT&T (local phone) | Local phone company | – |
| 815-455 | AT&T (local phone) | Local phone company | – |
| 815-459 | AT&T (local phone) | Local phone company | – |
| 815-477 | AT&T (local phone) | Local phone company | – |
| 815-479 | AT&T (local phone) | Local phone company | – |
| 815-526 | Teleport Communications America | Internet / business phone carrier | – |
| 815-788 | AT&T (local phone) | Local phone company | 2001 |
| 815-893 | Comcast | Internet / business phone carrier | 2004 |
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.