| | | Adams County | IL | 17001 | | Quincy, IL-MO 39500 | Quincy-Hannibal, IL-MO 448 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=AdamsCounty+IL |
| | | Boone County | IL | 17007 | | Rockford, IL 40420 | Rockford-Freeport-Rochelle,
IL 466 | Central | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=BooneCounty+IL |
| | | Bureau County | IL | 17011 | | Ottawa, IL 36837 | Chicago-Naperville,
IL-IN-WI 176 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=BureauCounty+Illinois |
| | | Champaign County | IL | 17019 | | Champaign-Urbana, IL 16580 | Champaign-Urbana-Denville,
IL 169 | Central | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=ChampaignCounty+IL |
| | | Christian County | IL | 17021 | | Taylorville, IL 45380 | Springfield-Jacksonville-Lincoln,
IL 522 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=ChristianCounty+IL |
| | | Coles County | IL | 17029 | | Charleston-Mattoon, IL 16660 | | Central | nonmetro county (rural) | federal/state
government-dependent | https://maps.google.com/?q=ColesCounty+IL |
| | | Cook County | IL | 17031 | Chicago-Naperville-Schaumburg,
IL 16984 | Chicago-Naperville-Elgin,
IL-IN 16980 | Chicago-Naperville,
IL-IN-WI 176 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=CookCounty+IL |
| | | DuPage County | IL | 17043 | Chicago-Naperville-Schaumburg,
IL 16984 | Chicago-Naperville-Elgin,
IL-IN 16980 | Chicago-Naperville,
IL-IN-WI 176 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=DuPageCounty+IL |
| | | Effingham County | IL | 17049 | | Effingham, IL 20820 | | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=EffinghamCounty+IL |
| | | Fulton County | IL | 17057 | | Canton, IL 15900 | Peoria-Canton, IL 427 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=FultonCounty+IL |
