| Code | Name | Region |
|---|---|---|
| USVNE | Mulvane | KS |
| USTM9 | Mumford | TX |
| USMUB | Muncie | IL |
| USMIE | Muncie | IN |
| USUNE | Muncie | KS |
| USMUN | Muncy | PA |
| USMUJ | Mundelein | IL |
| USUIP | Mountain View | MO |
| USMOU | Mountain Village | AK |
| USMSJ | Mountainside | NJ |
| USMMV | Mountainville | NJ |
| USHHF | Mountainville | NY |
| USXJI | Mountlake Terrace | WA |
| USZMM | Mounts Mills | NJ |
| USTVU | Mountville | GA |
| USXJH | Mountville | PA |
| USUTV | Mountville | SC |
| USMO4 | Mouth Of Wilson | VA |
| USMC7 | Mouthcard | KY |
| USM5O | Moville | IA |
| USYMQ | Moweaqua | IL |
| USXXE | Moxee City | WA |
| USIPG | Moyie Springs | ID |
| USM4Y | Moyock | NC |
| USMST | Muenster | TX |
| USH98 | Muhlenberg | PA |
| USMKI | Mukilteo | WA |
| USTGM | Mountain Green | UT |
| USVMV | Mountain Grove | MO |
| USWMH | Mountain Home | AR |
| USMUO | Mountain Home | ID |
| USMHU | Mountain Home | NC |
| USMUM | Mountain Home | TN |
| USHPQ | Mountain House | CA |
| USUII | Mountain Iron | MN |
| USML5 | Mountain Lake | MN |
| USUTK | Mountain Lake Park | MD |
| USULS | Mountain Lakes | NJ |
| USMTS | Mountain Pass | CA |
| USM6O | Mountain Ranch | CA |
| USMU5 | Mountain Rest | SC |
| USMUV | Mountain Top | PA |
| USMUL | Mountain View | AL |
| USVAJ | Mountain View | AR |
| USNUQ | Mountain View | CA |
| USMUK | Mountain View | GA |
| US5MV | Mountain View | HI |
| USMXH | Mount Vernon | IN |
| USMXV | Mount Vernon | KY |
| USUEO | Mount Vernon | ME |