| | | Menard County | TX | 48327 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=MenardCounty+TX |
| | | Medina County | TX | 48325 | | San Antonio-New
Braunfels, TX 41700 | San Antonio-New
Braunfels-Kerrville, TX 484 | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=MedinaCounty+TX |
| | | McMullen County | TX | 48311 | | | | | nonmetro county (rural) | mining-dependent | https://maps.google.com/?q=McMullenCounty+TX |
| | | McLennan County | TX | 48309 | | Waco, TX 47380 | | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=McLennanCounty+TX |
| | | McCulloch County | TX | 48307 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=McCullochCounty+TX |
| | | Maverick County | TX | 48323 | | Eagle Pass, TX 20580 | | Central | nonmetro county (rural) | federal/state
government-dependent | https://maps.google.com/?q=MaverickCounty+TX |
| | | Matagorda County | TX | 48321 | | Bay City, TX 13060 | Houston-Pasadena, TX 288 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=MatagordaCounty+TX |
| | | Mason County | TX | 48319 | | | | | nonmetro county (rural) | mining-dependent | https://maps.google.com/?q=MasonCounty+TX |
| | | Martin County | TX | 48317 | | Midland, TX 33260 | Midland-Odessa-Andrews,
TX 372 | Outlying | metro county (urban) | farm-dependent | https://maps.google.com/?q=MartinCounty+TX |
| | | Marion County | TX | 48315 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=MarionCounty+TX |
