| Code | Name | Region |
|---|---|---|
| USARI | Arcadia | FL |
| USJLM | Arcadia | IN |
| USAIQ | Arcadia | LA |
| USJDI | Arcadia | MO |
| USARZ | Arcadia | SC |
| USADI | Arcadia | WI |
| USVUM | Arcanum | OH |
| USACV | Arcata | CA |
| USAOP | Apopka | FL |
| USXAV | Appalachia | VA |
| USAPQ | Apple Creek | OH |
| USXAU | Apple Grove | WV |
| USAPV | Apple Valley | CA |
| USYAW | Apple Valley | MN |
| USAPR | Applegarth | NJ |
| USYPL | Applegate | OR |
| USAPP | Appleton | MN |
| USAUP | Appleton | NY |
| USATW | Appleton | WI |
| USAP7 | Appling | GA |
| USXAX | Appomattox | VA |
| USAPO | Aptos | CA |
| USAQO | Aquebogue | NY |
| USRAB | Arab | AL |
| USAJF | Arabi | GA |
| USAQX | Arabi | LA |
| USYGN | Aragon | GA |
| USRG4 | Aragonite | UT |
| USUBN | Antigo | WI |
| USANZ | Antioch | CA |
| USTIH | Antioch | IL |
| USTIO | Antioch | TN |
| USANT | Antler | ND |
| USATE | Antlers | OK |
| USANX | Antonia | MO |
| USZJK | Antonito | CO |
| USAH3 | Antrim | NH |
| USA6N | Antwerp | NY |
| USZAQ | Antwerp | OH |
| USANV | Anvik | AK |
| USAKG | Anza | CA |
| USA77 | Apache | OK |
| USAPJ | Apache Junction | AZ |
| USAAF | Apalachicola | FL |
| USAPI | Apalachin | NY |
| USAPX | Apex | NC |
| USZAP | Apollo | PA |
| USZAB | Apollo Beach | FL |
| USQAJ | Annapolis Junction | MD |
| USANN | Annette Island | AK |