| Code | Name | Region |
|---|---|---|
| USNXT | Pinconning | MI |
| USJPN | Pine | AZ |
| USPIQ | Piedmont | MO |
| USPIJ | Piedmont | SC |
| USS78 | Piedmont | SD |
| USPNT | Piedmont | WV |
| USPGN | Piegan | MT |
| USPJK | Pierce | ID |
| USP7N | Pierce | NE |
| USAZ8 | Pierce City | MO |
| USP8N | Pierceton | IN |
| USPR4 | Piercy | CA |
| USPI3 | Piermont | NH |
| USR9Y | Piermont | NY |
| USPIR | Pierre | SD |
| USPPQ | Pierre Part | LA |
| USPIF | Pierson | FL |
| USRZB | Pierz | MN |
| USPFY | Piffard | NY |
| USPIG | Pigeon | MI |
| USPF5 | Pigeon Falls | WI |
| USYPF | Pigeon Forge | TN |
| USXPN | Phoenix | IL |
| USP2X | Phoenix | MD |
| USXH5 | Phoenix | NY |
| USONX | Phoenix | OR |
| US5JD | Phoenix | TX |
| USPXT | Phoenix Township | AR |
| USPXV | Phoenixville | PA |
| USPIC | Picacho | AZ |
| USPY5 | Picatinny Arsenal | NJ |
| USPCU | Picayune | MS |
| USP3R | Picher | OK |
| USLQK | Pickens | SC |
| USYKV | Pickensville | AL |
| USJPK | Pickering | MO |
| USPXQ | Pickerington | OH |
| USP3T | Pickstown | SD |
| USPQU | Pico Rivera | CA |
| USXPI | Piedmont | AL |
| USPVK | Piedmont | CA |
| USPIX | Piedmont | KS |
| USPHP | Philip | SD |
| USPPI | Philippi | WV |
| USIIP | Philipsburg | MT |
| USZPC | Philipsburg | PA |
| US8LH | Phillips | ME |
| USPH9 | Phillips | NE |
| USPJP | Phillips | WI |
| USPHJ | Phillipsburg | KS |