Prefix 312-564 — Chicago Zone 01, IL

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

The 312-564 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.

Code-holder of record: FIRST COMMUNICATIONS, LLC (OCN 460K), assigned November 13, 2006. The prefix is pooled: its ten thousands-blocks can be shared among several carriers, so different 312-564 numbers may be served by different companies.

Caller ID showing 312-564 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

FAQ

Where is 312-564 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 312-564 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 312-564 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.