| | Mercer County | MO | 29129 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=MercerCounty+MO |
| | McDonald County | MO | 29119 | | | | | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=McDonaldCounty+MO |
| | Marion County | MO | 29127 | | Hannibal, MO 25300 | Quincy-Hannibal, IL-MO 448 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=MarionCounty+MO |
| | Maries County | MO | 29125 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=MariesCounty+MO |
| | Madison County | MO | 29123 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=MadisonCounty+MO |
| | Macon County | MO | 29121 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=MaconCounty+MO |
| | Livingston County | MO | 29117 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=LivingstonCounty+MO |
| | Linn County | MO | 29115 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=LinnCounty+MO |
| | Lincoln County | MO | 29113 | | St. Louis, MO-IL 41180 | St. Louis-St.
Charles-Farmington, MO-IL 476 | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=LincolnCounty+MO |
| | Lewis County | MO | 29111 | | Quincy, IL-MO 39500 | Quincy-Hannibal, IL-MO 448 | Outlying | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=LewisCounty+MO |