In 1673, when the French explorer and Jesuit priest, Father Marquette, reached the mouth of the Missouri River, he encountered the Osage Nation living on the western banks of the Mississippi River. This is the first recorded meeting between the Osage and Europeans. Forced westward by successive waves of European immigrants, 1847 found the tribe in Kansas. In 1865, the Osage agreed to the sale of their Kansas lands and to the purchase of a permanent home in Indian Territory, now Osage County, Oklahoma. The Osage moved there in 1872. Oil was discovered in 1898, which made a census necessary. Each member of the tribe was assigned one headright. These are inheritable and saleable within the tribe.