Mussellshell is located along the Mussellshell River in the central portion of the state. The town was first established as a crossing in 1877 for herds of Texas longhorns on their way to Montana owners. Later the crossing connected the Fort Custer and Fort Maginnis trail. The Mussellshell River was given its name when it was noted on the Lewis and Clark expedition that mussel shells were found along the river bed.
Mussellshell is located in central area of Montana, on US Highway 12 east of Roundup.