| Code | Name | Region |
|---|---|---|
| USICI | Mill City | NV |
| USZMK | Mill Creek | OK |
| USMC3 | Mill Creek | PA |
| USMKW | Mill Creek | WA |
| USMHP | Mill Hall | PA |
| USXRG | Mill Spring | MO |
| USTMJ | Mill Spring | NC |
| USVYV | Mill Valley | CA |
| USWM4 | Milladore | WI |
| USMBA | Millbrae | CA |
| USMBJ | Millbrook | AL |
| USZOO | Millbrook | NY |
| USXIR | Millburn | NJ |
| USMBT | Millbury | MA |
| USM4F | Mildford | MA |
| USJMD | Mildred | PA |
| USYMI | Miles City | FL |
| USMLS | Miles City | MT |
| USUQY | Milesburg | PA |
| USIVZ | Milesville | SD |
| USMFX | Milford | CT |
| USMEQ | Milford | DE |
| USMFJ | Milford | IA |
| USMFF | Milford | IL |
| USMII | Milford | IN |
| USMFK | Milford | MA |
| USMFO | Milford | ME |
| USMF5 | Milford | MI |
| USKMF | Milford | NE |
| USMFW | Milford | NH |
| USMFT | Milford | NJ |
| USQFD | Milford | NY |
| USMRQ | Milford | OH |
| USMFQ | Milford | PA |
| USIDW | Midwest City | OK |
| USIFB | Mifflinburg | PA |
| USM2I | Mifflintown | PA |
| USMFN | Mifflinville | PA |
| USML4 | Milaca | MN |
| USML7 | Milan | GA |
| USMIQ | Milan | IL |
| USNMM | Milan | IN |
| USYIM | Milan | KS |
| USUQZ | Milan | MI |
| USOML | Milan | MO |
| US9MI | Milan | NH |
| USMN9 | Milan | NM |
| US7ML | Milan | NY |
| USLIM | Milan | OH |
| USZIM | Milan | PA |