| | | McDonough County | IL | 17109 | | Macomb, IL 31380 | | Central | nonmetro county (rural) | federal/state
government-dependent | https://maps.google.com/?q=McDonoughCounty+IL |
| | | Massac County | IL | 17127 | | Paducah, KY-IL 37140 | Paducah-Mayfield, KY-IL 424 | Outlying | nonmetro county (rural) | recreation | https://maps.google.com/?q=MassacCounty+IL |
| | | Mason County | IL | 17125 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=MasonCounty+IL |
| | | Marshall County | IL | 17123 | | Peoria, IL 37900 | Peoria-Canton, IL 427 | Outlying | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=MarshallCounty+IL |
| | | Marion County | IL | 17121 | | Centralia, IL 16460 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=MarionCounty+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 |
| | | 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 |
| | | Macon County | IL | 17115 | | Decatur, IL 19500 | | Central | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=MaconCounty+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 |
| | | Livingston County | IL | 17105 | | Pontiac, IL 38700 | Bloomington-Pontiac, IL 145 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=LivingstonCounty+IL |
