Area Code 312 January 18, 2021 allcitycodes Telephone Codes 0 Where is area code 312 located? Below you will find a list of all cities covered by area code 312 in Illinois. Chicago, IL Read more:Area Code 718Area Code 815Area Code 810Area Code 816Area Code 812Area Code 804Area Code 813Area Code 715Area Code 770Area Code 719