Founded in 1826, Marion County is one of 114 counties in the state of Missouri. Historically, Marion County was formed from Ralls County. The city of Palmyra is the county seat. With FIPS code of 127, Marion County has a population of 28,518 and area of 438 square miles (1,134 km2).
List of all cities in Marion County, MO alphabetically
| City/Town | Postal Code | Area Code |
| Clay, MO | 63401 | 573 |
| Ely, MO | 63461 | 573 |
| Hannibal, MO | 63401 | 573 |
| Huntington, MO | 63401 | 573 |
| Ilasco, MO | 63401 | 573 |
| Maywood, MO | 63454 | 573 |
| Monkey Run, MO | 63401 | 573 |
| Palmyra, MO | 63461 | 573 |
| Philadelphia, MO | 63463 | 573 |
| Rensselaer, MO | 63401 | 573 |
| South River, MO | 63461 | 573 |
| Spalding, MO | 63401 | 573 |
| Taylor, MO | 63471 | 573 |
| West Ely, MO | 63401 | 573 |
| West Quincy, MO | 63471 | 573 |
| Withers Mill, MO | 63401 | 573 |
| 63461 | 573 | |
| Woodland, MO | 63461 | 573 |