Dhegihan Osage A Midwestern Native American tribe of the Great Plains. The tribe developed in the Ohio and Mississippi river valleys around 700 BCE along with other groups of its language family. They migrated west of the Mississippi after the 17th century CE due to wars with Iroquois invading the Ohio Valley from New York and Pennsylvania in a search for new hunting grounds. The nations separated at that time, and the Osage settled near the confluence of the Missouri and Mississippi rivers. Osages