| Code | Name | Region |
|---|---|---|
| USPKB | Parkersburg | WV |
| USP9R | Paradise | KS |
| US3PL | Paradise | PA |
| USVPD | Paradise | TX |
| USPDV | Paradise Valley | AZ |
| USP2V | Paradise Valley | NV |
| USQPG | Paragon | IN |
| USPGR | Paragould | AR |
| USPMQ | Paramount | CA |
| USPRM | Paramus | NJ |
| USPZM | Parchment | MI |
| USPDF | Pardeeville | WI |
| USPS5 | Paris | AR |
| USPRP | Paris | IL |
| USPZT | Paris | KY |
| USP7S | Paris | ME |
| USPHT | Paris | TN |
| USPRX | Paris | TX |
| USP3H | Parish | FL |
| USPSU | Parish | NY |
| USKPZ | Park | KS |
| US4PA | Panama | CA |
| USP99 | Panama | IA |
| US5PO | Panama | OK |
| USPFN | Panama City | FL |
| USZQV | Panama City Beach | FL |
| USPKO | Pandora | OH |
| USPNU | Panguitch | UT |
| USPHY | Panhandle, Carson | TX |
| USPH4 | Panhandle, Cass | TX |
| USP77 | Panora | IA |
| USPHQ | Panorama City | CA |
| USTEG | Pantego | NC |
| USTCG | Pantego | TX |
| USIPO | Paoli | IN |
| USVPI | Paoli | OK |
| USAOL | Paoli | PA |
| USWPO | Paonia | CO |
| USIOX | Papillion | NE |
| USPHU | Parachute | CO |
| USPD9 | Paradise | CA |
| USPBJ | Palmyra | NJ |
| USPZQ | Palmyra | NY |
| USPYY | Palmyra | PA |
| USPA7 | Palmyra | VA |
| USZPY | Palmyra | WI |
| US5PA | Palo | IA |
| USPAO | Palo Alto | CA |
| USFQO | Palo Cedro | CA |
| USPGZ | Palo Pinto | TX |