The term 'City of Northern Illinois' can be broken down into two crossword solutions: Elgin (5 letters) and DeKalb (6 letters). Elgin is a city located in Kane and DuPage counties in the northern part of Illinois. It is about 40 miles northwest of Chicago and is part of the Chicago metropolitan area. DeKalb is a city in DeKalb County, Illinois, located about 65 miles west of Chicago. It is the county seat of DeKalb County and is also part of the Chicago metropolitan area.