St. Louis is the second-largest city in Missouri, United States. It sits near the confluence of the Mississippi and the Missouri Rivers, on the western bank of the latter. As of 2020, the city proper had a population of around 301,500, while the bi-state metropolitan area, which extends into Illinois, had an estimated population of over 2.8 million, making it the largest metropolitan area in Missouri, the second-largest in Illinois, the seventh-largest in the Great Lakes Megalopolis, and the 20th-largest in the United States.
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 France's 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 Lewis and Clark Expedition. In the 19th century, St.