Mummy Cave rock shelter was home to Native Americans for nearly 10,000 years. It formed when the Shoshone River undercut a vertical cliff and then migrated south, after which the shelter began filling with sediment and slopewash. Its southern exposure provided a comfortable, temporary dwelling for prehistoric inhabitants of this valley. Excavations funded by the National Geographic Society in the 1960's revealed at least 38 layers of habitation, dating from 7,000 BC to the early 19th century. Most layers contained thousands of pieces of chipped stone, bone, and tools. Leather, basketry, wood, and shells were also preserved because of the dry conditions within the cave. The site is a key source for establishing the region's prehistoric cultural chronology.