Ash Hollow State Historical Park in western Nebraska preserves two linked places, Ash Hollow Cave and Windlass Hill, that together trace both long human occupation and overland travel into the North Platte valley. A spring near the cave made it a stopping place for centuries, and archaeology shows use by at least four indigenous cultures over more than 1,500 years, later followed by Lakota Sioux occupation. Near Ash Hollow in September 1855, about 600 United States Army troops attacked a Brule Sioux encampment, killing 86 people and capturing 70 women and children. Windlass Hill also preserves visible Oregon-California Trail wagon ruts on the steep descent into the valley.