The Mandan (Man-dun), though without an English equivalent, might have meant "those who tattooed themselves." They were one of the first tribes encountered by white settlers along the mouth of the Missouri River. The earliest recorded contact with the Mandan is recorded in the diary of the French Explorer Sieur de la Verendrye. In 1738 he wrote of a large compound of nine villages. A substantial depletion of the Mandan was evident by 1804, when Lewis and Clark discovered only two remaining villages standing.

Known to be a friendly tribe, they were open to trading goods with Euro-American explorers. Their heavy contact with explorers made them vulnerable to disease, resulting in the great smallpox epidemic of 1837. The epidemic left only 200 Mandan living, leading to a merger with the Hidatsa and Arikara Tribes of North Dakota. Today, there are over 1200 Mandan Indians living in the Great Plains region.

James Thompson