| | Clark County | IL | 17023 | | | | | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=ClarkCounty+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 |
| | 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 |
| | Cass County | IL | 17017 | | | | | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=CassCounty+IL |
| | Carroll County | IL | 17015 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=CarrollCounty+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 |
| | 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 |
| | Brown County | IL | 17009 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=BrownCounty+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 |
| | 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 |