The area code 312 is located in Chicago, Illinois.
Area code 312 serves the heart of Chicago, Illinois, covering downtown and nearby neighborhoods along Lake Michigan. It includes the city’s core business and cultural districts, such as the Loop, River North, Streeterville, the West Loop, and the South Loop. This central coverage makes 312 closely tied to Chicago’s skyline, finance, arts, dining, and shopping—especially along the Magnificent Mile. Chicago is in the Central Time Zone, and 312 phone numbers are widely recognized across the city and beyond.
Introduced in 1947, 312 was one of the original North American Numbering Plan area codes serving Chicago. In 1989, the suburbs split off into 708, and in 1996, the city itself split, creating 773 for outer Chicago neighborhoods while 312 remained downtown. To add capacity, the 872 overlay was introduced in 2009, so 312 and 872 now cover the same central area, and 10‑digit dialing is required across Chicago. These changes helped meet demand as Chicago’s population and businesses grew.
“Area code 312 was one of the original area codes created in 1947.” — North American Numbering Plan Administrator (NANPA)
Landmarks within the 312 area include:
A 312 phone number signals a downtown Chicago presence, often used by companies, cultural institutions, and service providers in the city’s core. If you see an 872 number in the same neighborhoods, it’s part of the overlay and functions the same way as 312. For visitors and locals alike, 312 connects to many of Chicago’s most famous sights and its busiest commercial corridors.