Chicago Zone 04, IL — rate center
- State
- Illinois
- Active prefixes
- 108
- Carriers
- 26
- Pooled prefixes
- 71
- LATA
- 358
- Metro area
- Chicago-Naperville-Elgin, IL-IN MSA
In NANP numbering, Chicago Zone 04, Illinois is a rate center — the anchor point for local numbers. It is reached through 312, 773, 872 (multiple area codes serve it).
The rate center currently carries 108 working prefixes, held by 26 different carriers. Pooling applies to 71 of them — individual thousands-blocks may belong to different companies.
The rate center belongs to the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area. Routing-wise it sits in LATA 358.
Because 312, 773, 872 all serve this territory, two Chicago Zone 04 numbers can look completely different while being neighbors — check the prefix, not just the area code.
Chicago Zone 04 ranks among the larger numbering localities in Illinois: 108 prefixes mean over 1,080,000 assignable numbers anchored here.
A Chicago Zone 04 prefix on caller ID is a starting point, not proof of origin — numbers travel with their owners and displays can be spoofed. Use official callback numbers for anything sensitive.
Prefixes anchored to Chicago Zone 04
| Prefix | Code holder | Pooled |
|---|---|---|
| 312-735 | T-MOBILE USA, INC. | Yes |
FAQ
What area code is Chicago Zone 04, IL?
Chicago Zone 04 is served by 3 area codes — 312, 773, 872 — which overlay the same territory.
How many prefixes does Chicago Zone 04 have?
108 active NXX prefixes are anchored to this rate center in NANPA records, held by 26 carriers.
Is a call from a Chicago Zone 04 prefix really from Chicago Zone 04?
Not necessarily. The prefix marks where the number block was issued; porting, VoIP and spoofing all detach calls from that geography.