The sudden arrival of the Lewis and Clark  Expedition among the tribes as a result of the Louisiana Purchase was an event that forever changed the lives and cultural trajectory of every Native American Nation West of the Mississippi River.  Of course, the Eastern tribes were still dealing with the changing situations brought on by the Euro-American invasion and had been for more than two hundred years.  It all happened slowly enough that, at first, most of the Indian leaders did not give the idea of sharing their lands with non-natives serious thought.  But, soon enough, the continual and growing immigration became a worrisome source of anger and a threat to lifestyle and security for Native Peoples.  It did not take too long before the situation boiled over and general hostilities became the normal expectation.

The Mandan lived in partially excavated dwellings framed with logs and covered by a thick layer of soil.  They were quite roomy dwellings and good protection against the heat of summer and the cold of winter.  Unlike most other plains tribes, they did not move their villages constantly about in hunting food.  Like the Hidatsa and Arikara, with whom they are today federated as one tribe, they farmed small crops and hunted buffalo and other game but traded their crops for meat as well. Their villages became well-used trading Marts for tribes even hundreds of miles away.  They were a rich culture that was decimated by the Small Pox introduced to them by traders prior to the arrival of Lewis and Clark.  The L & C expedition spent the winter with them peacefully in 1804 and it was there that the Captains met the Lemhi Shoshone woman, Sacagawea, who gave advice and provided service as guide during their epic journey to the Pacific Ocean and the return.