The U.S. state of Illinois is divided into ten distinct geographic numbering plan areas in the North American Numbering Plan (NANP), which are assigned a total of seventeen area codes.

Lookup area code information for CHICAGO, IL. Get the NPA NXX (area code and prefix) as well as much more data for CHICAGO, IL.

Where is area code 312? Area code 312 serves part of Chicago, IL. It overlaps coverage areas with area code 872.

Find 312 area code details including city, time zone, and map. Lookup area code 312 phone number, name, and location.

Mar 9, 2025 · Find out where 312 area code zone from, which states, counties and cities it covers. Get the most exact information on time zones here

Find the local area code for Chicago, Illinois. Our complete calling resource guide instantly gives you the the Chicago area code and local time to help you make your long distance call to …

This was a controversal spilt where everyone in the City of Chicago changed their area code except "Chicago Zone 01" - an area that covers the loop. This allowed major corporations …

3 days ago · Illinois - Area code 312 is currently assigned for use in Illinois since January 01, 1947. View all phone prefixes used in area code 312 or other area codes in Illinois.

What is an area code “overlay”? An “overlay” is when more than one area code serves the same geographic area. The City of Chicago has been served by area codes 312 and 773 since …

Area code 312 is a telephone area code in the North American Numbering Plan for the city of Chicago, including downtown, the Chicago Loop, and its immediate environs.