| | Woodford County | IL | 17203 | | Peoria, IL 37900 | Peoria-Canton, IL 427 | Central | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=WoodfordCounty+IL |
| | Winnebago County | IL | 17201 | | Rockford, IL 40420 | Rockford-Freeport-Rochelle,
IL 466 | Central | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=WinnebagoCounty+IL |
| | Williamson County | IL | 17199 | | Marion-Herrin, IL 32060 | Carbondale-Marion-Herrin,
IL 166 | Central | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=WilliamsonCounty+IL |
| | Will County | IL | 17197 | 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=WillCounty+IL |
| | Whiteside County | IL | 17195 | | Sterling, IL 44580 | Dixon-Sterling, IL 221 | Central | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=WhitesideCounty+IL |
| | White County | IL | 17193 | | | | | nonmetro county (rural) | mining-dependent | https://maps.google.com/?q=WhiteCounty+IL |
| | Wayne County | IL | 17191 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=WayneCounty+IL |
| | Washington County | IL | 17189 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=WashingtonCounty+IL |
| | Warren County | IL | 17187 | | | | | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=WarrenCounty+IL |
| | Wabash County | IL | 17185 | | | | | nonmetro county (rural) | mining-dependent | https://maps.google.com/?q=WabashCounty+IL |