Chicago, IL Area Codes

Area codes serving Chicago

Chicago sits in Illinois, part of the Midwest region and the Central Time zone. The Chicago area uses 3 area codes (312, 773, 872). They cover different parts of the metro — see the table below for which code serves where — and codes that share a territory are overlays of each other.

The original code is 312 (in service since 1947). As the area ran low on numbers, regulators added overlay codes on top instead of splitting the city, so longtime residents kept their numbers while new lines received a newer code.

Code	Area served	In service
312	Downtown Chicago, including the Loop and nearby central neighborhoods	January 1, 1947
773	The City of Chicago outside the downtown 312 area	October 12, 1996
872	The entire city of Chicago, overlaying both 312 (downtown) and 773 (the rest of the city)	November 7, 2009

How to pick an area code for a new number

When you activate a new line in Chicago, the carrier assigns whichever code has numbers available — you usually can't choose. If a specific code matters to you (for example the prestige of 312), ask the carrier whether any blocks remain, or request a number transfer. All codes here dial identically and cost the same.

Dialing in Chicago

Wherever two codes overlay the same ground, 10-digit dialing is mandatory. Dialing the full 10-digit number always works, so it is the safest habit across the whole metro. See 10-digit dialing and overlay area codes for the background. For every code in Illinois, visit the Illinois area codes page.