These are the people who traded with Lewis & Clark on the Missouri, and where they met the Shoshone woman, Sacajawea...
The Mandan and associated tribes were equestrian in habit and depended about equally on hunting and agriculture, cultivating large fields of corn, beans, pumpkins, and sunflowers (for the edible seeds), which they traded to the Plains tribes for horses and buffalo robes.
According to Maximilian the Mandan were vigorous, well made, rather above medium stature, many of them being broad-shouldered and muscular. They paid the greatest attention to their headdress.
Tattooing was practised to a limited extent, mostly on the left breast and arm, with black parallel stripes and a few other figures.
Some of the women were robust and rather tall, though usually they were short and broad-shouldered, and were adept potters.
Their houses were large circular communal structures of stout logs covered with earth, and their villages were sometimes palisaded.
They had the same organization of military societies common to the Plains tribes generally.
Polygamy was common.
Besides the Sun and the Buffalo, they invoked a number of supernatural personages, among whom was the "Old Woman who Never Dies," who presided over the fields and harvests, and in whose honour they performed ritual dances and sacrifices at planting and gathering.
They had numerous shrines and sacred places, and their great palladium was a sacred "ark," which was connected with their genesis myth, and which was carefully guarded in a house by itself.
Their great ceremony of the Sun Dance — described by Catlin under the name of Okeepa — exceeded that of all other tribes in the extent of barbarous self-torture practised by the participants.
The Mandan tribe was reduced to a scant 130 members due to smallpox..