The Osage Nation has a rich and varied geographic history. Our origins lie in the Ohio River valley, and we slowly migrated toward our modern day territory in Northeast Oklahoma. A visual of this migration can be seen on our ancestral map and if you're interested in which modern territories were our homeland throughout history, take a look at this list of States and Counties.
A more detailed summary of our ancestral geography is provided below, courtesy of Dr. Andrea A. Hunter.
Ancestral Osage Geography
The following summary of Osage and ancestral Osage geography is derived from archaeological data, oral traditions, historical, and linguistic evidence provided in this report to prove a shared group identity between the Clarksville Mound Group inhabitants and the Osage Nation. The Osage are identified as a Dhegiha Siouan language speaking tribe along with the Omaha, Ponca, Kaw, and Quapaw. According to Osage and Dhegiha Siouan oral tradition, the origin of the Dhegiha Siouan tribes is in the Ohio River valley. During the Middle Woodland period, A.D. 200 to A.D. 400, the Dhegiha as a group, started migrating down the Ohio River valley to the confluence of the Mississippi and Ohio rivers. During the Late Woodland period, A.D. 400 to A.D. 500, the Dhegiha tribes (minus the Quapaw) migrated up the central Mississippi River valley settling in the St. Louis area as well as traveling outward from the valley following the various river drainages into the interior of what are now Missouri and Illinois. During the latter part of the Late Woodland (A.D. 900) and Emergent Mississippian, (A.D. 1000) periods, larger groups of the Dhegiha Siouan tribes focused their settlement strategy in the Cahokia/St. Louis area. At the onset of the Mississippian period, A.D. 1000, those who would later become the Omaha and Ponca tribes separated from the other two remaining Dhegiha Siouan tribes. At some point after the Omaha and Ponca departure, the Kaw separated and traveled up the Missouri River during the Middle Mississippian period, A.D. 1200-A.D. 1250. Those who would later become the Osage were the last remaining Dhegiha Siouan tribe in the Cahokia/St. Louis area. At the end of the Mississippian period, A.D. 1300, the Osage shifted their settlement pattern and moved westward to focus primarily within the central and western portions of the state of Missouri. At the onset of the historic period large groups of the Osage were located along the Missouri and Osage rivers.
Above excerpt is from: Osage Nation NAGPRA Claim for Human Remains Removed from the Clarksville Mound Group (23PI6), Pike County, Missouri
Andrea A. Hunter, James Munkres, and Barker Fariss, Osage Nation Historic Preservation Office, Pawhuska, OK (2013) pp. 1-60.