| | | Jackson County | IL | 17077 | | Carbondale, IL 16060 | Carbondale-Marion-Herrin,
IL 166 | Central | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=JacksonCounty+IL |
| | | Jefferson County | IL | 17081 | | Mount Vernon, IL 34500 | | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=JeffersonCounty+IL |
| | | Kane County | IL | 17089 | Elgin, IL 20994 | Chicago-Naperville-Elgin,
IL-IN 16980 | Chicago-Naperville,
IL-IN-WI 176 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=KaneCounty+IL |
| | | Kankakee County | IL | 17091 | | Kankakee, IL 28100 | Chicago-Naperville,
IL-IN-WI 176 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=KankakeeCounty+IL |
| | | Kendall County | IL | 17093 | Elgin, IL 20994 | Chicago-Naperville-Elgin,
IL-IN 16980 | Chicago-Naperville,
IL-IN-WI 176 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=KendallCounty+IL |
| | | Knox County | IL | 17095 | | Galesburg, IL 23660 | | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=KnoxCounty+IL |
| | | Lake County | IL | 17097 | Lake County, IL 29404 | Chicago-Naperville-Elgin,
IL-IN 16980 | Chicago-Naperville,
IL-IN-WI 176 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=LakeCounty+IL |
| | | LaSalle County | IL | 17099 | | Ottawa, IL 36837 | Chicago-Naperville,
IL-IN-WI 176 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=LaSalleCounty+Illinois |
| | | Lee County | IL | 17103 | | Dixon, IL 19940 | Dixon-Sterling, IL 221 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=LeeCounty+IL |
| | | Livingston County | IL | 17105 | | Pontiac, IL 38700 | Bloomington-Pontiac, IL 145 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=LivingstonCounty+IL |
