| Code | Name | Region |
|---|---|---|
| USXZM | Morrisville | NC |
| USMV9 | Morrisville | NJ |
| USMZL | Morrisville | NY |
| USXIO | Morrisville | PA |
| USORS | Morrisville | VT |
| USMJK | Morro Bay | CA |
| USMRW | Morrow | GA |
| USVJM | Morganville | NJ |
| USMY5 | Moriarty | NM |
| USZH6 | Moriches | NJ |
| US2MR | Moriches | NY |
| USJGM | Morley | MO |
| USOYO | Moro | AR |
| USO4O | Moro | IL |
| USXOO | Moro | OR |
| USOOC | Morocco | ID |
| USMR6 | Moroni | UT |
| USMJC | Morral | OH |
| USXWQ | Morrice | MI |
| USRQR | Morrill | ME |
| USMOK | Morrill | NE |
| USMPJ | Morrilton | AR |
| USXRI | Morris | AL |
| USMR4 | Morris | CT |
| USMSW | Morris | IL |
| USMR3 | Morris | LA |
| USMOX | Morris | MN |
| USM9V | Moretown | VT |
| USNGM | Morgan | GA |
| USMRG | Morgan | MT |
| USMR9 | Morgan | PA |
| USGGM | Morgan | UT |
| US7MR | Morgan | VT |
| USMGN | Morgan City | AL |
| USLMO | Morgan City | LA |
| USPTN | Morgan City-patterson Apt | LA |
| USMJV | Morgan Hill | CA |
| US2MP | Morgan Point | TX |
| USQGF | Morganfield | KY |
| USMPP | Morgans Point | TX |
| USO99 | Morganton | GA |
| USMRN | Morganton | NC |
| USMGG | Morgantown | KY |
| USMJZ | Morgantown | NC |
| USMGP | Morgantown | PA |
| USMWG | Morgantown | TN |
| USMGW | Morgantown | WV |
| USMQK | Moorpark | CA |
| USMSZ | Moose Pass | AK |
| USUXB | Moosic | PA |