| | | 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 |
| | | 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 |
| | | 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 |
| | | Monroe County | IL | 17133 | | St. Louis, MO-IL 41180 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=MonroeCounty+IL |
| | | Morgan County | IL | 17137 | | Jacksonville, IL 27300 | Springfield-Jacksonville-Lincoln,
IL 522 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=MorganCounty+IL |
| | | Ogle County | IL | 17141 | | Rochelle, IL 40300 | Rockford-Freeport-Rochelle,
IL 466 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=OgleCounty+IL |
