6/24/2006:
On this day in 1837, the steamboat St. Peter arrived at the Fort Union trading post at the confluence of the Missouri and Yellowstone Rivers. It had traveled up the Missouri River from Fort Clark. The steamboat’s arrival at the forts was to trigger one of the largest smallpox outbreaks among Native Americans in American history. Although aware that the infection was onboard, crewmembers hoped that it would not spread from the vessel. It soon became apparent that their hopes were in vain as the disease quickly spread through the fort. Francis Chardon, the bourgeois in charge of the nearby Fort Clark, attempted to prevent its spread to the surrounding tribes by closing the forts, but the Native Americans camped nearby anyhow in hopes of obtaining valuable trade goods. The first Mandan died on July 14 from the infection, and by August 31, Chardon estimated a death toll of 800 from the Mandan tribe alone. Chardon himself lost a two-year old son in the epidemic, which in the end killed 90% of the Mandan and 50% of the Hidatsa tribes.
The two depleted nations later united with surviving Arikaras and settled at Like-A-Fishhook Point. Fort Union was completely abandoned in 1867.
Sources:
Lounsberry, Col. Clement A. North Dakota History and People, Volume I. S.J. Clarke Publishing Company; Chicago; 1916.
http://lewisandclark.state.mt.us/sites.asp
http://home.att.net/~mman/StPetersSmallPox
http://www.lewisandclark200.gov/plw/northdakota