 <unk> used the Missouri , at least to a limited extent , as a path of trade and transport . In addition , the river and its tributaries formed tribal boundaries . <unk> of the indigenous mostly centered on a semi @-@ nomadic culture ; many tribes would have different summer and winter camps . However , the center of Native American wealth and trade lay along the Missouri River in the Dakotas region on its great bend south . A large cluster of walled Mandan , Hidatsa and <unk> villages situated on <unk> and islands of the river was home to thousands , and later served as a market and trading post used by early French and British explorers and fur traders . Following the introduction of horses to Missouri River tribes , possibly from feral European @-@ introduced populations , natives ' way of life changed dramatically . The use of the horse allowed them to travel greater distances , and thus facilitated hunting , communications and trade . 
