St. Peter's Mission had no fixed address for its first two decades. The Jesuits established it in 1859 at Priest Butte on the Teton River, near present-day Choteau. When a local herder was killed by Blackfeet within sight of the mission in April 1860, the priests moved downstream. They kept moving - following the shrinking borders of the Blackfeet Indian Reservation as the federal government forced the tribe to cede more land. By 1877, the mission consisted of just two one-room log cabins, one doubling as a church. The priests spent most summers traveling with nomadic Blackfeet bands across the plains. In 1881, the mission finally settled at its permanent location on Birch Creek, where soldiers from nearby Fort Shaw helped the priests build a log chapel that doubled as sleeping quarters.

Bishop Jean-Baptiste Brondel invited the Ursuline order to join the Jesuits at St. Peter's in January 1884. Mother Mary Amadeus, born Sarah Therese Dunne in Ohio, led five nuns to Montana that October. The Jesuits gave them $200 in provisions, some cows, wagons, and a farm - and a promise of $200 per year if they would teach the boys. The nuns quickly established a girls' boarding school. When Mother Amadeus fell gravely ill with pneumonia in April 1885, word reached the Ursuline convent in Toledo. Mary Fields, a former slave who had worked for the Dunne family, accompanied Mother Stanislaus to Montana to nurse her friend. Fields stayed, becoming indispensable to mission operations despite - or perhaps because of - her unconventional ways.

In 1883, Father Joseph Damiani offered a teaching position to a controversial figure: Louis Riel, the Metis leader who had led resistance movements against Canadian expansion. Riel, his wife Marguerite, and their son Jean-Louis had been living with nomadic Metis bands. With Marguerite pregnant, Riel decided to settle down. From December 1883, he taught English, French, mathematics, and practical skills - wood carving, metalworking, leather making - to 22 to 25 Metis boys at St. Peter's. The student body soon changed as A'aninin and Piegan Blackfeet boarding students arrived in growing numbers. Riel would leave St. Peter's to lead the Northwest Rebellion in Canada, for which he was executed in 1885.

The mission grew into an impressive complex. A four-story stone boys' school with a mansard roof rose in 1887. Philadelphia heiress Katharine Drexel - later canonized as a saint - donated $5,000 for a three-story stone convent completed in 1892. An 'opera house' for musical performances opened in 1896. But federal funding cuts forced the Jesuits to abandon St. Peter's in 1898. The Ursulines continued alone until a fire in January 1908 destroyed the boys' school, priests' residence, and several outbuildings. A second fire in November 1918 consumed the girls' school, ending the mission's educational work. Today, the expanded chapel and the red wooden opera house - now used as a barn - still stand on private ranch land. The cemetery lies uphill behind the chapel, surrounded by a buck fence to keep cattle away, its graves marked by tall monuments, ornate iron fences, and headstones hidden in the high grass.