| Code | Name | Region |
|---|---|---|
| USFFJ | Moffett | OK |
| USMEF | Moffett Field | CA |
| USMGD | Mogadore | OH |
| US3MO | Mohall | ND |
| USMY7 | Mohave Valley | AZ |
| USM67 | Mohawk | NY |
| USOH9 | Mohegan Lake | NY |
| USZOH | Mohnton | PA |
| USOH7 | Mohrsville | PA |
| USMOJ | Mojave | CA |
| USM7K | Mokane | MO |
| USIMK | Mokena | IL |
| USMOL | Molalla | OR |
| USM47 | Molena | GA |
| USMLI | Moline | IL |
| USMSO | Missoula | MT |
| USURI | Missouri City | MO |
| USMC5 | Missouri City | TX |
| USIFV | Missouri Valley | IA |
| USM5I | Miston | TN |
| USM2L | Mitchell | AL |
| USMHC | Mitchell | IN |
| USMC9 | Mitchell | MS |
| USMIH | Mitchell | NE |
| USMHE | Mitchell | SD |
| USITX | Mitchellville | IA |
| USIHE | Mitchellville | MD |
| USXIZ | Mize | KY |
| USCNY | Moab | UT |
| USOAP | Moapa | NV |
| USVIZ | Moatsville | WV |
| USMBY | Moberly | MO |
| USMOB | Mobile | AL |
| USMBG | Mobridge | SD |
| USMKV | Mocksville | NC |
| USMI2 | Mio | MI |
| USIQU | Miquon | PA |
| USMIK | Mira Loma | CA |
| USMLM | Mira Mesa | CA |
| USM89 | Miracle | KY |
| USMMR | Miramar | FL |
| USIBC | Miramar Beach | FL |
| USNJK | Miranda | CA |
| USIRL | Mirror Lake | NH |
| USNCE | Misenheimer | NC |
| USMCJ | Mishawaka | IN |
| USJMZ | Mishicot | WI |
| USMSI | Mission | KS |
| US4MS | Mission | SD |
| USZMX | Mission | TX |