Founded in Mar 1, 1810, Madison County is one of 88 counties in the state of Ohio. Historically, Madison County was formed from Franklin County. The city of London is the county seat. With FIPS code of 97, Madison County has a population of 44,386 and area of 465.44 square miles (1,205 km2).
List of all cities in Madison County, OH alphabetically
| City/Town | Postal Code | Area Code |
| London, OH | 43140 | 740 |
| Mount Sterling, OH | 43143 | 740 |
| Plain City, OH | 43064 | 614/380 |
| Sedalia, OH | 43151 | 740 |
| South Solon, OH | 43153 | 937 |
| Summerford, OH | 43140 | 740 |
| West Jefferson, OH | 43162 | 740 |