Linguistic, archaeological, and mythological data present an unclear picture of precontact Osage history. The Osage, Kansa, Omaha, Ponca, and Quapaw collectively constitute the Dhegihan Siouan speakers. These languages are so close as to be mutually intelligible. The myths of these groups describe a westward migration out of the Ohio valley and define the order in which the groups split off from one another. Precisely when this migration took place is not clear, since archaeological data seem to indicate that the Osage had lived in southwestern Missouri for some time prior to French Contact in 1673. Native groups bordering the Osage in 1673 included the Caddoan-speaking Pawnee, Wichita, and Mento in the Arkansas River valley to the south and west, the Siouan-speaking Oto, Missouri, and Kansa along the Missouri River to the north and west, and the Algonkian-speaking Illini peoples far to the east along the Mississippi River. During the early historic period, Osage relations with most of these peoples were volatile. The greatest conflict was with the Caddoan-speaking peoples with whom they were at war from the late seventeenth until the late nineteenth centuries. Starting in the 1680s, the Osage were in regular Contact with French traders, whose supply of guns made them the most militarily powerful tribe in French Louisiana.
In 1803 Louisiana was purchased by the United States. To find homes for dislocated eastern tribes as well as European-American settlers, the United States negotiated a series of treaties with the Osage. In 1808 the Osage ceded most of their lands in present-day Missouri and Arkansas. The Western Cherokee were given a reservation in Arkansas and quickly came into conflict with the Osage over hunting territory. In 1817 a Cherokee war party attacked an Osage Village, killing eighty-three men, women, and children and taking over one hundred captive. The following year a new treaty was negotiated, and the Osage ceded much of eastern Oklahoma. In 1821 the Cherokee again attacked an Osage village, and in 1825 a new treaty ceded all the Osage lands except for a tract in what is now southern Kansas.
In 1870 the Osage agreed to allow the government to sell their Kansas reservation to White settlers for $1.25 per acre. Part of the money was used to purchase a new, smaller Reservation in Indian Territory (Oklahoma), where they moved in 1871. The remainder of the money was deposited in the U.S. Treasury, and the interest used for the betterment of the Osage. In 1897 oil was discovered on the Osage reservation. In 1906 the Osage allotment act was passed, and the reservation opened to White settlers. Surface rights were divided among tribal members, but the tribe retained and still retains title to mineral rights, including the vast oil and natural gas deposits. The Osage reservation also retained its legal status as an allotted reservation.