File:Fire-destroyed Ursuline Convent - St Peters Mission - Near Cascade Montana - 1918.jpg
St. Peter's was founded by priests belonging to the Society of Jesus (the Jesuits), a Roman Catholic men's religious order. It was established at Bird Tail Rock in 1871 after several previous locations were abandoned. Ursuline nuns joined the mission in October 1884 to assist in running the mission and teaching Native American children.
In 1884, the mission consisted of two log buildings -- a chapel with a bell tower connected to a common sleeping area for priests, and a lower structure which consisted of a sleeping area for nuns and a kitchen. A three-story wooden boys' school, a stone convent for the Ursulines (which included classrooms for girls), bake house, laundry, chicken yard, barn, opera house, and corral were built over the next 25 years.