In which county of Montana is the Historic St. Mary's Mission located? 
St. Mary's Mission (Montana): The Historic St. Mary’s Mission is a mission established by the Society of Jesus of the Catholic Church; located now on 4th street in modern-day Stevensville, Montana. Stevensville, Montana: Stevensville (Salish: ɫq̓éɫmlš) is a town in Ravalli County, Montana, United States.
Ravalli County, Montana