The Missouri River Valley, up to this location, was well-known to French and British fur trappers. For decades, trappers navigated down the Big Sioux River and the lower Missouri toward St. Louis. Due to the intimidating presence of the Yankton and Teton Sioux, the fur trade dwindled upriver from the mouth of the Big Sioux.
President Jefferson instructed the Corps of Discovery to seek out Indian tribes and record their languages, populations, religions, customs, food, clothing, and especially their willingness to trade with the United States. Given one desertion, a fatality, and four court-martials with less than one fourth of the journey completed, Meriwether Lewis and William Clark were anxious as they prepared to fulfill Jefferson's orders by meeting with representatives of the Sioux Nations for the first time.
Corps of Discovery first saw the conical tipis, used by the nomadic Northern Plains Indians, at the Yankton Sioux encampment.
The Mysterious Mound
Strange stories abounded in this unfamiliar territory. One legend just 20 miles upriver involved a lone prairie hill in habited by 18-inch-high "Deavels" armed with "Sharp arrows with which they Can Kill at a great distance." The Indian tribes were said to avoid this hill, known
today as Spirit Mound.
"..above the Bluff we had the Prairie Set on fire to let the Soues See that we were on the river and as a Signal for them to Come to it."
William Clark, August 27, 1804