Prefix 312-319 — Chicago Zone 01, IL

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

Area code
312
Prefix (NXX)
319
Rate center
Chicago Zone 01
State
Illinois
Time zone
Central
Code holder
MCIMETRO ACCESS TRANSMISSION SERVICES LLC
OCN
7229
Pooled
Yes (thousands-block pooling)
Assigned
2017-04-28
LATA
358

A phone number starting 312-319 was issued in the Chicago Zone 01 rate center of IL — part of area code 312.

The assigned code holder is MCIMETRO ACCESS TRANSMISSION SERVICES LLC, operating company number 7229, assigned April 28, 2017. This is a pooled prefix — expect numbers within it to be split across more than one carrier in 1,000-number blocks.

A scammer can display 312-319 without ever touching IL. When in doubt, end the call and reach the company or agency through its official website; unwanted robocalls belong in the FTC's fraud report queue.

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.

Neighboring prefixes

Prefixes adjacent to 312-319
PrefixRate centerCode holder
312-316 Chicago Zone 01 NEW CINGULAR WIRELESS PCS, LLC - IL
312-317 Wheeling NEW CINGULAR WIRELESS PCS, LLC - IL
312-318 La Grange CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL
312-320 Chicago Zone 01 NEW CINGULAR WIRELESS PCS, LLC - IL
312-321 Chicago Zone 01 ILLINOIS BELL TEL CO
312-322 Chicago Zone 01 ILLINOIS BELL TEL CO

FAQ

Where is 312-319 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 312-319 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 312-319 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.