Area Code 312 History - Illinois

Significant events for area code 312


Year
Details
1947 One of the four original area codes for Illinois. It covered the Chicago metro area.
1989 Area code 312 was split with 708 covering the Chicago suburbs.
1996 Area code 312 was split with 773 covering all of the area outside of downtown Chicago.
2009 Area code 872 was overlaid on 312 and 773 .