| Code | Name | Region |
|---|---|---|
| USQXO | Monroeville | NJ |
| USO8M | Monroeville | OH |
| USVML | Monroeville | PA |
| USXIY | Monrovia | CA |
| USON5 | Monrovia | IN |
| USOMH | Monmouth | IA |
| USMNI | Monmouth | IL |
| USMOH | Monmouth | ME |
| USOO9 | Monmouth | OR |
| USM9O | Monmouth Beach | NJ |
| USMJU | Monmouth Junction | NJ |
| USOON | Monon | IN |
| USMXJ | Monona | IA |
| USIMO | Monona | WI |
| USMXX | Monongahela | PA |
| USMOM | Monroe | CT |
| USMOE | Monroe | GA |
| USNRQ | Monroe | IA |
| USINQ | Monroe | IN |
| USMLU | Monroe | LA |
| US9OE | Monroe | ME |
| USMOI | Monroe | MI |
| USMNR | Monroe | NC |
| USM4X | Monroe | NH |
| USOWH | Monroe | NJ |
| US7MO | Molt | MO |
| USMME | Momence | IL |
| US4MU | Mona | UT |
| USMNP | Monaca | PA |
| USMIF | Monahans | TX |
| USM4V | Monaville | WV |
| USMNK | Moncks Corner | SC |
| USMQ2 | Monclova | OH |
| USMCP | Moncure | NC |
| USODI | Mondovi | WI |
| USQZE | Monee | IL |
| USQJU | Monessen | PA |
| USMQG | Moneta | VA |
| USTTF | Monett | KS |
| USMMO | Monett | MO |
| USM6T | Monetta | SC |
| USQTE | Monette | AR |
| USOES | Money | MS |
| US2KN | Monkton | MD |
| US7MK | Monkton | VT |
| USMEY | Modena | PA |
| USOJX | Modena | WI |
| USMOD | Modesto | CA |
| USM98 | Modoc | IN |
| USMA3 | Moffat | CO |