Founded in Mar 1, 1818, Clark County is one of 88 counties in the state of Ohio. Historically, Clark County was formed from Champaign, Madison, and Greene Counties. The city of Springfield is the county seat. With FIPS code of 23, Clark County has a population of 135,633 and area of 399.86 square miles (1,036 km2).
List of all cities in Clark County, OH alphabetically
| City/Town | Postal Code | Area Code |
| Catawba, OH | 43010 | 937 |
| Donnelsville, OH | 45319 | 937 |
| Enon, OH | 45323 | 937 |
| Medway, OH | 45341 | 937 |
| New Carlisle, OH | 45344 | 937 |
| North Hampton, OH | 45349 | 937 |
| Selma, OH | 45368 | 937 |
| South Charleston, OH | 45368 | 937 |
| South Vienna, OH | 45369 | 937 |
| Springfield, OH | 45501 | 937 |
| 45502 | 937 | |
| 45503 | 937 | |
| 45504 | 937 | |
| 45505 | 937 | |
| 45506 | 937 | |
| Tremont City, OH | 45372 | 937 |