Assuming you meant Maritime State: the area near Chicago borders the Great Lakes, which is a series of interconnected freshwater lakes - so not maritime.
Chicago,IL
US area code 872 is Chicago, IL, overlaying 312 and 773.
The Great Lakes Naval Training Station is in Lake County, IL. Lake County is the northeasternmost county in Illinois.
800 miles
833 miles
Springfield, IL utilizes one area code which is area code 217.
Bloomington/Normal, IL, is in area code 309.
29-30 miles
About 1200 miles
Oak Brook, Illinois, is in area code 630 and overlay code 331.
area code: 630 or 331 (331 is an overlay on 630)