| Code | Name | Region |
|---|---|---|
| USCF5 | Clam Falls | WI |
| USCGU | Clam Gulch | AK |
| USZCY | Clancy | MT |
| USQCT | Clanton | AL |
| USZCC | Clara City | MN |
| US9CE | Clare | IA |
| USQAI | Clare | IL |
| USXRE | Clare | MI |
| USC5C | Cibecue | AZ |
| USZCB | Cibolo | TX |
| USXDN | Cicero | IL |
| USC9O | Cicero | IN |
| USCCC | Cicero | NY |
| USCM8 | Cimarron | CO |
| USCI2 | Cincinnati | KY |
| USCVG | Cincinnati | OH |
| USXDU | Cinnaminson | NJ |
| USIRC | Circle | AK |
| USCHP | Circle Hot Springs | AK |
| USZLP | Circle Pines | MN |
| USC7V | Circleville | KS |
| USCIE | Circleville | OH |
| USIEV | Circleville | UT |
| USCIS | Cisco | TX |
| US9CS | Cisne | IL |
| US8CS | Cissna Park | IL |
| USIRA | Citra | FL |
| USCIT | Citronelle | AL |
| US6CV | Christmas Valley | OR |
| USIPH | Christopher | IL |
| USHYM | Chrome | NJ |
| USCL3 | Chualar | CA |
| USCHU | Chuathbaluk | AK |
| USUCK | Chubbuck | ID |
| USCCK | Chuckatuck | VA |
| USZCF | Chuckey | TN |
| USCHR | Chugiak | AK |
| USCUV | Chula Vista | CA |
| USCU4 | Chunchula | AL |
| USUFB | Church Hill | MO |
| USCRH | Church Hill | TN |
| USHCP | Church Point | LA |
| USJJP | Churchtown | PA |
| USHQC | Churchville | MD |
| USICJ | Churchville | NY |
| USCCH | Churchville | VA |
| USUUO | Churubusco | IN |
| USUUB | Churubusco | NY |
| USCGO | Chittenango | NY |
| US7TT | Chittenden | VT |