The landslide occurred on June 23, 1925, following melt from a heavy snowpack, several weeks of heavy rain, and earthquake tremors in the area. Approximately of primarily sedimentary rock slid down the north face of Sheep Mountain, crossed over the Gros Ventre River and rode up the opposite mountainside a distance of . The landslide created a large dam over high and wide across the Gros Ventre River, backing up the water and forming Lower Slide Lake.