Mosby is on the east bank of the Musselshell River. It was named for William Henry Mosby, who settled here in 1891 after coming over the Rocky Mountains by team and wagon from Cottage Grobe, Oregon. The community was formerly known as Baldwin, but the Mosby familyand the post officemoved down the river with the post office set up in the Mosby home. (from Cheney's Names on the Face of Montana, Mountain Press Publishing Company)
The town was initially developed as homesteaders came to claim their 160 acres of free land. However, it was a harsh existence and many homesteaders moved on. Oil wells have been developed in the Cat Creek area.
