The Siouan Tribe is a Native American tribe that is composed of several different tribes, including the Otoe (4 letters), Iowa (4 letters), Oglalas (7 letters), Osage (5 letters), Omaha (5 letters), Omahas (6 letters), and Missouri (8 letters). These tribes are located in the Great Plains region of the United States and Canada. They have a long history of trading and cultural exchange with other Native American tribes.