| | Lawrence County | IL | 17101 | | | | | nonmetro county (rural) | mining-dependent | https://maps.google.com/?q=LawrenceCounty+IL |
| | 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 |
| | Logan County | IL | 17107 | | Lincoln, IL 30660 | Springfield-Jacksonville-Lincoln,
IL 522 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=LoganCounty+IL |
| | McDonough County | IL | 17109 | | Macomb, IL 31380 | | Central | nonmetro county (rural) | federal/state
government-dependent | https://maps.google.com/?q=McDonoughCounty+IL |
| | McHenry County | IL | 17111 | 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=McHenryCounty+IL |
| | McLean County | IL | 17113 | | Bloomington, IL 14010 | Bloomington-Pontiac, IL 145 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=McLeanCounty+IL |
| | Macon County | IL | 17115 | | Decatur, IL 19500 | | Central | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=MaconCounty+IL |
| | Macoupin County | IL | 17117 | | St. Louis, MO-IL 41180 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=MacoupinCounty+IL |
| | Madison County | IL | 17119 | | St. Louis, MO-IL 41180 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=MadisonCounty+IL |