| Code | Name | Region |
|---|---|---|
| USKSC | Cascade | ID |
| USC4U | Cascade | MD |
| USCDA | Cascade | MT |
| USCZK | Cascade Locks | OR |
| USCS3 | Casco | ME |
| USCC4 | Casco | MI |
| USZQO | Casco | WI |
| USC83 | Caseville | MI |
| USAJY | Casey | IL |
| USCV9 | Caseyville | IL |
| USCS2 | Cash | AR |
| USCJS | Cashiers | NC |
| USC4S | Cashion | AZ |
| USXEI | Cashmere | WA |
| USCN9 | Cashton | WI |
| USCSO | Casnovia | MI |
| USCPR | Casper | WY |
| USCCP | Caspian | MI |
| USAV7 | Carterville | LA |
| USRTG | Carthage | IL |
| USCAW | Carthage | IN |
| USCJQ | Carthage | MO |
| USCGT | Carthage | MS |
| USTAG | Carthage | NC |
| USQCH | Carthage | NY |
| USCGX | Carthage | TN |
| USCJP | Carthage | TX |
| USUHQ | Caruthers | CA |
| USAHV | Caruthersville | MO |
| USYCE | Carver | MA |
| USCXB | Carver | OR |
| USLXL | Carville | LA |
| USAYI | Cary | IL |
| USCFC | Cary | NC |
| USXEN | Caryville | TN |
| USJCJ | Casa Blanca | NM |
| USCGZ | Casa Grande | AZ |
| USFCS | Casar | NC |
| USCQR | Carrollton | OH |
| USCAX | Carrollton | TX |
| USQLN | Carrollton | VA |
| USDCW | Carrolltown | PA |
| USC97 | Carrs Corner | NJ |
| USCRU | Carson | CA |
| USRNM | Carson | MS |
| US5ON | Carson | ND |
| USC5S | Carson | NM |
| USRZQ | Carson | WA |
| USCSN | Carson City | NV |
| USCSU | Carsonville | MI |