Sonnette is located just outside of Custer National Forest along Pumpkin Creek. Sonnette was first established by a trapper and buffalo hunter Charles Mason, and the area was known as Camps Pass. Later, the community was known as Selway and came to be called Sonnette when the post office was established in 1926.
Sonnette is located in south eastern area of Montana, to the east of Broadus off of US Highway 212.