Founded in February 11, 1911, Musselshell County is one of 56 counties in the state of Montana. Historically, Musselshell County was formed from Fergus County, Meagher County, and Yellowstone County. The city of Roundup is the county seat. With FIPS code of 65, Musselshell County has a population of 4,896 and area of 1,867 square miles (4,836 km2).
List of all cities in Musselshell County, MT alphabetically
| City/Town | Postal Code | Area Code |
| Delphia, MT | 59073 | 406 |
| Klein, MT | 59072 | 406 |
| Melstone, MT | 59054 | 406 |
| Musselshell, MT | 59059 | 406 |
| Roundup, MT | 59072 | 406 |
| 59073 | 406 |