| | | Christian County | IL | 17021 | | Taylorville, IL 45380 | Springfield-Jacksonville-Lincoln,
IL 522 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=ChristianCounty+IL |
| | | Clark County | IL | 17023 | | | | | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=ClarkCounty+IL |
| | | Clay County | IL | 17025 | | | | | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=ClayCounty+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 |
| | | 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 |
| | | Crawford County | IL | 17033 | | | | | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=CrawfordCounty+IL |
| | | Cumberland County | IL | 17035 | | Effingham, IL 20820 | | Outlying | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=CumberlandCounty+IL |
| | | De Witt County | IL | 17039 | | | | | metro county (urban) | nonspecialized | https://maps.google.com/?q=DeWittCounty+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 |
