Founded in Apr 1, 1820, Mercer County is one of 88 counties in the state of Ohio. Historically, Mercer County was formed from Darke County. The city of Celina is the county seat. With FIPS code of 107, Mercer County has a population of 42,309 and area of 463.27 square miles (1,200 km2).
List of all cities in Mercer County, OH alphabetically
| City/Town | Postal Code | Area Code |
| Burkettsville, OH | 45310 | 419/567 |
| Carthagena, OH | 45822 | 419/567 |
| Celina, OH | 45822 | 419/567 |
| Celina, OH | 45826 | 419/567 |
| Chickasaw, OH | 45826 | 419/567 |
| Coldwater, OH | 45828 | 419/567 |
| Fort Recovery, OH | 45846 | 419/567 |
| Maria Stein, OH | 45860 | 419/567 |
| Mendon, OH | 45862 | 419/567 |
| Montezuma, OH | 45866 | 419/567 |
| Rockford, OH | 45882 | 419/567 |
| Saint Henry, OH | 45883 | 419/567 |