| | | McLennan County | TX | 48309 | | Waco, TX 47380 | | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=McLennanCounty+TX |
| | | McMullen County | TX | 48311 | | | | | nonmetro county (rural) | mining-dependent | https://maps.google.com/?q=McMullenCounty+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 |
| | | Menard County | TX | 48327 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=MenardCounty+TX |
| | | Midland County | TX | 48329 | | Midland, TX 33260 | Midland-Odessa-Andrews,
TX 372 | Central | metro county (urban) | mining-dependent | https://maps.google.com/?q=MidlandCounty+TX |
| | | Milam County | TX | 48331 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=MilamCounty+TX |
| | | Mills County | TX | 48333 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=MillsCounty+TX |
| | | Mitchell County | TX | 48335 | | | | | nonmetro county (rural) | federal/state
government-dependent | https://maps.google.com/?q=MitchellCounty+TX |
| | | Montague County | TX | 48337 | | | | | nonmetro county (rural) | mining-dependent | https://maps.google.com/?q=MontagueCounty+TX |
| | | Montgomery County | TX | 48339 | | Houston-Pasadena-The
Woodlands, TX 26420 | Houston-Pasadena, TX 288 | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=MontgomeryCounty+TX |
