Without artwork like the Swiss artist Karl Bodmer’s Fort Union on the Missouri, Fort Union Trading Post National Historic Site would not exist today and the nation might not have a National Park Service (NPS). Circulated widely in the middle 1800s, prints of paintings by Bodmer and his contemporary George Catlin transformed people’s attitudes toward the Great Plains. This Bodmer painting is Fort Union’s most famous, and but one of many he made while touring the Upper Missouri with his employer, German naturalist Prince Maximilian of Wied. With assistance from the American Fur Company, which owned Fort Union, Bodmer and Maximilian produced the most thorough ethnographic record of the Upper Missouri tribes from the 1800s, including the Assiniboine shown here trading and camping at Fort Union in 1833. At Fort Union, Native Americans traded bison robes, beaver pelts, and other furs for imported manufactured goods such as cloth and guns, which transformed the Plains Indians’ cultures and lifeways. This confluence of cultures at the country’s longest operating fur trade post (1828–1867) inspired Congress to establish the national historic site in 1966 and later to fund reconstruction of the post. Bodmer’s painting proved vital to historians and architects who reconstructed the post between 1987 and 1993, as did the extensive 1980s archeological excavations that recovered hundreds of thousands of fort-era artifacts that are now curated at the park. Combined with archeological discoveries, these illustrations provided the evidence needed to design and build the most accurate reconstruction possible.