Founded in 1824, Clinton County is one of 102 counties in the state of Illinois. Historically, Clinton County was formed from Washington, Bond, and Fayette County. The city of Carlyle is the county seat. With FIPS code of 27, Clinton County has a population of 36,793 and area of 474 square miles (1,228 km2).
List of all cities in Clinton County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Albers, IL | 62215 | 618/730 |
| Aviston, IL | 62216 | 618/730 |
| Bartelso, IL | 62218 | 618/730 |
| Beckemeyer, IL | 62219 | 618/730 |
| Boulder, IL | 62231 | 618/730 |
| Breese, IL | 62216 | 618/730 |
| 62230 | 618/730 | |
| Carlyle, IL | 62231 | 618/730 |
| Clement, IL | 62252 | 618/730 |
| Damiansville, IL | 62215 | 618/730 |
| Ferrin, IL | 62231 | 618/730 |
| Germantown, IL | 62245 | 618/730 |
| Hoffman, IL | 62250 | 618/730 |
| Huey, IL | 62252 | 618/730 |
| Irishtown, IL | 62253 | 618/730 |
| Keyesport, IL | 62253 | 618/730 |
| New Baden, IL | 62265 | 618/730 |
| New Memphis, IL | 62266 | 618/730 |
| Posey, IL | 62231 | 618/730 |
| Royal Lake, IL | 62231 | 618/730 |
| Saint Morgan, IL | 62293 | 618/730 |
| Saint Rose, IL | 62230 | 618/730 |
| Santa Fe, IL | 62218 | 618/730 |
| Shattuc, IL | 62231 | 618/730 |
| Shatuc, IL | 62231 | 618/730 |
| Sugar Creek, IL | 62293 | 618/730 |
| Tamalco, IL | 62253 | 618/730 |
| Trenton, IL | 62216 | 618/730 |
| 62293 | 618/730 |