Evidence exists that native peoples traveled through Oklahoma as early as the last ice age. Ancestors of the Wichita and Caddo lived in what is now Oklahoma. The Panhandle culture peoples were precontact residents of the panhandle region. The westernmost center of the Mississippian culture was Spiro Mounds, in what is now Spiro, Oklahoma, which flourished between AD 850 and 1450. Spaniard Francisco Vásquez de Coronado traveled through the state in 1541, but French explorers claimed the area in the 1700s and it remained under French rule until 1803, when all the French territory west of the Mississippi River was purchased by the United States in the Louisiana Purchase.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): When did France sell Oklahoma's land to the US?
1803