From the record
“Peter's Mission Church and Cemetery, also known as St. Peter's-By-the-Rock is a historic Roman Catholic mission located on Mission Road 10.5 miles (16.9 km) west-northwest of the town of Cascade, Montana, United States.”
Wikipedia article St. Peter's Mission Church and Cemetery, CC BY-SA 4.0.
One of 43 National Register listings published here for Cascade County · listed in 1984 · category: Building.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service · the Wikipedia article