Prefix 312-506 — Chicago Zone 01, IL

NANPA CO code assignment, current as of July 28, 2026.

Area code
312
Prefix (NXX)
506
Rate center
Chicago Zone 01
State
Illinois
Time zone
Central
Code holder
FIRST COMMUNICATIONS, LLC
OCN
460K
Pooled
Yes (thousands-block pooling)
Assigned
2004-05-24
LATA
358

The 312-506 prefix belongs to area code 312 and is anchored to the Chicago Zone 01 rate center (IL). In NANP terms, the prefix — or NXX — determines the rate center a number is billed against.

Chicago Zone 01 is part of the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area. For routing purposes it sits in LATA 358. Numbers here keep Central time.

NANPA's central-office code records list FIRST COMMUNICATIONS, LLC (OCN 460K) as the code holder, assigned May 24, 2004. Because 312-506 participates in thousands-block pooling, individual 1,000-number blocks may belong to other carriers than the code holder.

Caller ID showing 312-506 is not proof the call came from Chicago Zone 01: spoofing and porting both detach numbers from their origin. To verify a caller, hang up and dial the organization's published number, and report suspicious calls to the FTC.

Neighboring prefixes

Prefixes adjacent to 312-506
PrefixRate centerCode holder
312-503 Chicago Zone 01 TELEPORT COMMUNICATIONS AMERICA, LLC - IL
312-504 Chicago Zone 01 NEW CINGULAR WIRELESS PCS, LLC - IL
312-505 Chicago Zone 01 CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL
312-507 Chicago Zone 01 ILLINOIS BELL TEL CO
312-508 Chicago Zone 01 PEERLESS NETWORK OF ILLINOIS, LLC - IL
312-509 Chicago Zone 01 PEERLESS NETWORK OF ILLINOIS, LLC - IL

FAQ

Where is 312-506 located?

The prefix is assigned to the Chicago Zone 01 rate center in IL, area code 312. It is part of the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area.

Which company owns 312-506 numbers?

FIRST COMMUNICATIONS, LLC holds the code, but the prefix is pooled — individual thousands-blocks can be assigned to other carriers, and numbers may be ported to any provider.

Is a call from 312-506 safe to answer?

The prefix itself says nothing about the caller. Legitimate Chicago Zone 01 businesses and spoofed robocalls can both display it. Never share personal data with an unverified inbound caller.