The history of St. Louis, Missouri began with the settlement of the St. Louis area by Native American mound builders who lived as part of the Mississippian culture from the 9th century to the 15th century, followed by other migrating tribal groups. Starting in the late 17th century, French explorers arrived. Spain took over in 1763 and a trading company led by Pierre Laclede and Auguste Chouteau established the settlement of St. Louis in February 1764. It attracted French settlers leaving Illinois after their defeat in the Seven Years' War. The city grew in population due to its location as a trading post on the Mississippi River, as the western fur trade was lucrative. The city played a small role in the American Revolutionary War and became part of the U.S. through the Louisiana Purchase