St. Louis () is the second-largest city in Missouri, United States. It is located near the confluence of the Mississippi and the Missouri rivers. In 2020, the city proper had a population of 301,578, while its bi-state metropolitan area, which extends into Illinois, had an estimated population of over 2.8 million. It is the largest metropolitan area in Missouri and the second largest in Illinois. Before European settlement, the area had been occupied for thousands of years by various Native American cultures. From roughly 900 to 1500 CE, it was a regional center of Mississippian culture, based in Cahokia east of the river, and extending across the continent along the Mississippi and its tributaries. St. Louis was founded on February 14, 1764, by French fur traders Gilbert Antoine de St. Maxent, Pierre Laclède and Auguste Chouteau, all from New Orleans. They named it for king Louis IX of France, and it quickly became the regional center of the French Illinois Country. In 1764, France was defeated in the Seven Years' War and was forced to cede its territory east of the Mississippi to Great Britain. It ceded its nominal claim to areas west of the river to Spain. In 1800, Spain retroceded Louisiana to France. Three years later, Napoleon gave up on North America and sold the territory to the United States as part of the Louisiana Purchase.The city was the point of embarkation for the Corps of Discovery on the United States' sponsored Lewis and Clark Expedition to explore the Louisiana Purchase. In the 19th century, St. Louis developed as a major port on the Mississippi River; from 1870 until the 1920 census, it was the fourth-largest city in the country. It separated from St. Louis County in 1877, becoming an independent city and limiting its political boundaries. In 1904, it hosted the Louisiana Purchase Exposition (also known as the World's Fair) and the Summer Olympics. A global city with a metropolitan GDP of more than $160 billion in 2017, metropolitan St. Louis has a diverse economy with strengths in the service, manufacturing, trade, transportation, and tourism industries. It is home to eight Fortune 500 companies. Major companies headquartered or with significant operations in the city include Ameren Corporation, Peabody Energy, Nestlé Purina PetCare, Anheuser-Busch, Wells Fargo Advisors, Stifel Financial, Spire, Inc., MilliporeSigma, FleishmanHillard, Square, Inc., Anthem BlueCross and Blue Shield, Centene Corporation, and Express Scripts. Federal agencies include the Federal Reserve Bank of St. Louis, U.S. Department of Agriculture offices, and National Geospatial-Intelligence Agency, which is developing a new headquarters here. Major research universities include Washington University in St. Louis, Saint Louis University and University of Missouri–St. Louis. The Washington University Medical Center in the Central West End neighborhood hosts an agglomeration of medical and pharmaceutical institutions, including Barnes-Jewish Hospital. St. Louis has four professional sports teams: the St. Louis Cardinals of Major League Baseball, the St. Louis Blues of the National Hockey League, St. Louis City SC of Major League Soccer, and the St. Louis BattleHawks of the XFL. Among the city's notable attractions are the 630-foot (192 m) Gateway Arch in Downtown St. Louis, the St. Louis Zoo, the Missouri Botanical Garden, the St. Louis Art Museum, and Bellefontaine Cemetery and Arboretum.