 Complete the following phrase:  Before European settlement, the area was a regional center of Native American Mississippian culture. St. Louis was founded on February 14, 1764, by French fur traders Gilbert Antoine de St. Maxent, Pierre Laclède and Auguste Chouteau, who named it for Louis IX of France. In 1764, following Frances defeat in the Seven Years War, the area was ceded to Spain. In 1800, it was retroceded to France, which sold it three years later to the United States as part of the Louisiana Purchase; the city was then the point of embarkation for the Corps of Discovery on the 