| Code | Name | Region |
|---|---|---|
| USCL7 | Carlisle, Spartanburg | SC |
| USC9A | Carlock | IL |
| USVAQ | Carlos | MN |
| USCLD | Carlsbad | CA |
| USCNM | Carlsbad | NM |
| USUAK | Carlstadt | NJ |
| US4CT | Carlton | GA |
| USLRH | Carlton | MN |
| USAOG | Carlton | OR |
| USYCR | Carlton | PA |
| USTE2 | Carlton | TX |
| USIYC | Carlyle | IL |
| US9SS | Carlyss | LA |
| USCRJ | Carman | NY |
| USZCA | Carmel | CA |
| USRML | Carmel | IN |
| USC9M | Carmel | ME |
| USCMZ | Carmel | NY |
| US9CB | Carbonville | UT |
| USCBY | Carbury | ND |
| USZBZ | Cardiff By The Sea | CA |
| US3OH | Cardington | OH |
| USEFQ | Carefree | AZ |
| USRCO | Carencro | LA |
| USCXJ | Carey | OH |
| USCRY | Careywood | ID |
| USCI5 | Caribou | CA |
| USCAR | Caribou | ME |
| USCPC | Carle Place | NY |
| USCNL | Carleton | MI |
| USCNV | Carlin | NV |
| USVCN | Carlinville | IL |
| USCUZ | Carlisle | AR |
| USC9S | Carlisle | IA |
| USCQI | Carlisle | IN |
| USCSJ | Carlisle | MA |
| USCI7 | Carlisle | NY |
| USCRL | Carlisle | OH |
| USCSP | Cape Spencer | AK |
| USCVI | Cape Vincent | NY |
| USCPZ | Capistrano Beach | CA |
| USCAP | Capitan | CA |
| USC6P | Capitan | NM |
| USACD | Capitol Heights | MD |
| USCGP | Capitola | CA |
| USCJ7 | Capron | IL |
| US9CC | Captain Cook | HI |
| US4CP | Captiva | FL |
| USC5P | Capulin | CO |
| US9TU | Caratunk | ME |