The Lewis and Clark Expedition built Fort Mandan on the Missouri River to protect them from the winter weather from 1805 to 1806. Though the original location is unknown and believed to be underwater, a replica fort sits 2 miles south of the Lewis and Clark Interpretive Center in Washburn, North Dakota. Visitors enjoy guided tours of this fort every 45 minutes, as of 2015.
Built in a triangular shape from cottonwood lumber harvested from the riverbanks of the Missouri, Fort Mandan featured high walls on all sides, an open interior space amid the structures and a fate that faced the Missouri River, the primary mode of travel for the Lewis and Clark Expedition. The Corps of Discovery began the project on Nov. 2, 1804 and remained inside the fort through April 7, 1805, according to journals by expedition members.
Since the fort sat slightly downriver from five villages associated with the Hidatsa and Mandan tribes, it took its name from them in honor of their hospitality and generosity of the Mandans. Though a harsh winter that dipped to roughly 45 degrees Fahrenheit made building the fort a necessity, diplomacy with friendly tribes also served as another impetus. By establishing friendly relations with various tribes and forming alliances with them against hostile Native Americans, such as the Tetons, the Lewis and Clark Expedition helped open trade routes that eventually led to the settlement of the West.