| Code | Name | Region |
|---|---|---|
| USMDZ | Moundridge | KS |
| US7Q9 | Mounds | IL |
| USOUK | Mounds | OK |
| USMJO | Mounds View | MN |
| USMFZ | Moundsville | WV |
| USMOA | Moundville | AL |
| USND5 | Moundville | MO |
| USNQU | Mount Airy | GA |
| USM8Y | Mount Airy | LA |
| USMYM | Mount Airy | MD |
| USMKY | Mount Airy | NC |
| USOMO | Mount Angel | OR |
| USUNM | Mount Arlington | NJ |
| USOUA | Mount Ayr | IA |
| USMJR | Mount Berry | GA |
| USMB5 | Mount Bethel | PA |
| USMXT | Mount Bethel | PA |
| USOEL | Moselle | MS |
| USKMY | Moser Bay | AK |
| USMWH | Moses Lake | WA |
| USMOS | Moses Point | AK |
| USEIB | Mosheim | TN |
| USYMR | Mosier | OR |
| USINX | Mosinee | WI |
| USMJN | Moss | TN |
| USZGA | Moss Beach | CA |
| USMLG | Moss Landing | CA |
| USMOG | Moss Point | MS |
| USMVJ | Mossville | IL |
| US89M | Mossyrock | WA |
| USMOF | Motley | MN |
| USMLL | Mottville | MI |
| USMUW | Moulton | AL |
| USX3L | Moulton | TX |
| USQUG | Moultonborough | NH |
| USMGR | Moultrie | GA |
| USOUD | Mound | MN |
| USMW6 | Morrow | OH |
| US4MT | Morse | TX |
| USMB3 | Morse Bluff | NE |
| USMTI | Morton | IL |
| USJMN | Morton | MN |
| USMNQ | Morton | MS |
| USJZN | Morton | PA |
| USZMT | Morton | TX |
| USOT3 | Morton | WA |
| USMGV | Morton Grove | IL |
| USMJJ | Mortons Gap | KY |
| USOQV | Morven | NC |
| USMW3 | Moscow | IA |