| Code | Name | Region |
|---|---|---|
| USM7E | Merchantville | NJ |
| USDRA | Mercury | NV |
| USMD5 | Meredith | NH |
| USENU | Mendon | MO |
| USM8N | Mendon | NY |
| USM2O | Mendon | UT |
| USZMC | Mendota | CA |
| USMEN | Mendota | IL |
| USDTB | Mendota | TX |
| USDO7 | Mendota | VA |
| USMDG | Mendota Heights | MN |
| USMN5 | Menemsha | MA |
| USEFE | Menifee | CA |
| USMNL | Menlo | GA |
| US5LO | Menlo | IA |
| USMKU | Menlo Park | CA |
| USMO6 | Menno | SD |
| USZME | Meno | OK |
| USMNM | Menominee | MI |
| USMMF | Menomonee Falls | WI |
| USMMM | Menomonie | WI |
| USMX9 | Mentmore | NM |
| USMT6 | Mentone | AL |
| USYJN | Melvin | TX |
| US9VL | Melvin Village | NH |
| USMGF | Melvindale | MI |
| USZGD | Memphis | FL |
| US8MI | Memphis | IN |
| USOMQ | Memphis | MI |
| USEJS | Memphis | MO |
| USEI2 | Memphis | MS |
| USMEM | Memphis | TN |
| USMTX | Memphis | TX |
| USAE4 | Mena | AR |
| USXXG | Menahga | MN |
| USNAD | Menands | NY |
| USMEZ | Menasha | WI |
| USQMQ | Mendenhall | MS |
| USZEY | Mendham | NJ |
| USMND | Mendocino | CA |
| USM6E | Mendon | IL |
| USNDO | Mendon | MA |
| USJJJ | Mendon | MI |
| USMYU | Mekoryuk | AK |
| USMKB | Melba | ID |
| USMQJ | Melbourne | AR |
| USMLB | Melbourne | FL |
| USZJG | Melbourne | IA |
| USMBE | Melbourne Beach | FL |
| USMFV | Melfa | VA |