| Code | Name | Region |
|---|---|---|
| USVMJ | Melissa | TX |
| USFG4 | Melissa | WV |
| USZML | Mellen | WI |
| USM34 | Mellenville | NY |
| USDMW | Mellwood | AR |
| USMLO | Melrose | MA |
| USMMZ | Melrose | MN |
| USM5L | Melrose | NY |
| USMO2 | Melrose | TN |
| USMRP | Melrose Park | IL |
| USEKU | Melrose Park | PA |
| USZMV | Melville | NY |
| USZVM | Melvin | IL |
| USNMZ | Medina | MN |
| USDQM | Medina | ND |
| USMDK | Medina | NY |
| USMDQ | Medina | OH |
| USDIN | Medina | TX |
| USVMX | Medina | WA |
| USEQH | Medinah | IL |
| USMDY | Medley | FL |
| USMN3 | Medon | TN |
| USMD6 | Medora | KS |
| USMY9 | Medway | MA |
| USM8A | Medway | ME |
| USDWF | Medway | OH |
| USMRU | Meeker | CO |
| USMK3 | Meeker | OK |
| USEM8 | Meeteetse | WY |
| USJJK | Megargel | TX |
| US32M | Meggett | SC |
| USMEH | Mehoopany | PA |
| USQIG | Meigs | GA |
| USHCG | Mechanicsburg | IL |
| USMEG | Mechanicsburg | PA |
| USECI | Mechanicsburg, Beaver | PA |
| USMEC | Mechanicsville | VA |
| USMHV | Mechanicville | NY |
| USUMQ | Mecosta | MI |
| US9MB | Meddybemps | ME |
| USMDC | Medfield | MA |
| USMFC | Medford | MA |
| USME4 | Medford | MN |
| USUQN | Medford | NJ |
| USMDE | Medford | NY |
| US3MD | Medford | OK |
| USMFR | Medford | OR |
| USMDF | Medford | WI |
| USMDR | Medfra | AK |
| USXIJ | Media | PA |