| Code | Name | Region |
|---|---|---|
| USZQR | Carter | KY |
| USTJQ | Carter | MT |
| USTQR | Carter | OK |
| USCTR | Carter Lake | IA |
| USCSF | Carteret | NJ |
| USUFK | Cartersville | GA |
| USVYZ | Cartersville | SC |
| US4CV | Carterville | IL |
| USCRV | Carpentersville | IL |
| USCPT | Carpinteria | CA |
| USB6V | Carrabasset Valley | ME |
| USCRB | Carrabelle | FL |
| USZRR | Carrboro | NC |
| USZ2B | Carrier | OK |
| USCM9 | Carrier Mills | IL |
| USTKX | Carriere | MS |
| USIGO | Carrington | ND |
| USCZT | Carrizo Springs | TX |
| USUFH | Carrizozo | NM |
| USCIN | Carroll | IA |
| USR9L | Carroll | NE |
| USCWU | Carroll | OH |
| USC2R | Carrollton | AL |
| USCRR | Carrollton | GA |
| USC5K | Carrollton | IL |
| USCRK | Carrollton | KY |
| USKJR | Carrollton | MI |
| USCR2 | Carrollton | MO |
| USCMV | Carmel Valley | CA |
| USMRY | Carmel-monterey Apt | CA |
| USQCM | Carmen | OK |
| USAMI | Carmi | IL |
| USCM3 | Carmichael | CA |
| USCXK | Carmichaels | PA |
| USC8R | Carmine | TX |
| USNGI | Carnegie | OK |
| USCRE | Carnegie | PA |
| USNAF | Carnelian Bay | CA |
| USC2A | Carnesville | GA |
| USAEY | Carneys Point | NJ |
| USCJO | Caro | MI |
| USCI3 | Carol City | FL |
| USACE | Carol Stream | IL |
| USICO | Carolina | RI |
| USOIQ | Carolina | WV |
| USKIQ | Carolina Beach | NC |
| USKCA | Caroline | WI |
| USCP5 | Carpenter | SD |
| USUFI | Carlisle | PA |
| USQLC | Carlisle | SC |