Prefix 312-585 — Chicago Zone 01, IL

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

Numbers in the 312-585 prefix are registered to the Chicago Zone 01 rate center in IL, inside area code 312. The prefix is the second block of a ten-digit US number (312-585-XXXX) and pins the number to a billing locality.

NANPA's central-office code records list MCIMETRO ACCESS TRANSMISSION SERVICES LLC (OCN 7229) as the code holder, assigned April 16, 2013. Because 312-585 participates in thousands-block pooling, individual 1,000-number blocks may belong to other carriers than the code holder.

The rate center lies in the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area. The serving LATA is 358. Local time follows the Central zone.

Spoofing means this prefix on your screen doesn't guarantee a Chicago Zone 01 caller. Verify independently before trusting a request for money or data.

Neighboring prefixes

FAQ

Where is 312-585 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 312-585 numbers?

MCIMETRO ACCESS TRANSMISSION SERVICES 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 312-585 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.