| | Alexander County | IL | 17003 | | Cape Girardeau, MO-IL 16020 | Cape Girardeau-Sikeston,
MO-IL 164 | Outlying | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=AlexanderCounty+IL |
| | Bond County | IL | 17005 | | St. Louis, MO-IL 41180 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Outlying | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=BondCounty+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 |
| | Calhoun County | IL | 17013 | | St. Louis, MO-IL 41180 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Outlying | metro county (urban) | farm-dependent | https://maps.google.com/?q=CalhounCounty+IL |
| | 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 |
| | Clinton County | IL | 17027 | | St. Louis, MO-IL 41180 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=ClintonCounty+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 |
| | DeKalb County | IL | 17037 | Elgin, IL 20994 | Chicago-Naperville-Elgin,
IL-IN 16980 | Chicago-Naperville,
IL-IN-WI 176 | Outlying | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=DeKalbCounty+IL |
| | De Witt County | IL | 17039 | | | | | metro county (urban) | nonspecialized | https://maps.google.com/?q=DeWittCounty+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 |