Plains Indians had seen horses. Later, they acquired horses from the Spanish, and rapidly radically altered their lifestyle and range. Following this transformation, the Kansa (sometimes Kaw) and Osage Nation (originally Ouasash) arrived in Kansas in the 17th century. (The Kansa claimed that they occupied the territory since 1673.) By the end of the 18th century, these two tribes were dominant in the eastern part of the future state: the Kansa on the Kansas River to the North and the Osage on the Arkansas River to the South. At the same time, the Pawnee (sometimes Paneassa) were dominant on the plains to the west and north of the Kansa and Osage nations, in regions home to massive herds of bison. Europeans visited the Northern Pawnee in 1719. In 1720, the Spanish military's Villasur expedition was wiped out by Pawnee and Otoe warriors near present-day Columbus, Nebraska, effectively ending Spanish expedition into the region. The French commander at Fort Orleans, Étienne de Bourgmont, visited the Kansas River in 1724 and established a trading post there, near the main Kansa village at the mouth of the river. Around the same time, the Otoe tribe of the Sioux also inhabited various areas around the northeast corner of Kansas. Louisiana Purchase Apart from brief explorations, neither France nor Spain had any settlement or military or other activity in Kansas. In 1763, following the Seven Years' War in which Great Britain defeated France, Spain acquired the French claims west of the Mississippi River. It returned this territory to France in 1803, keeping title to about . In the Louisiana Purchase of 1803, the United States (US) acquired all of the French claims west of the Mississippi River; the area of Kansas was unorganized territory. In 1819 the United States confirmed Spanish rights to the as part of the Adams–Onís Treaty with Spain. That area became part of Mexico, which also ignored it. After the Mexican–American War and the US victory, the United States took over that part in 1848. The Lewis and Clark Expedition left St. Louis on a mission to explore the Louisiana Purchase all the way to the Pacific Ocean. In 1804, Lewis and Clark camped for three days at the confluence of the Kansas and Missouri rivers in what is today Kansas City, Kansas (today commemorated at the Kaw Point Riverfront Park). They met French fur traders and mapped the area. In