St. Louis () is an independent city in the U.S. state of Missouri. 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. The city's combined statistical area (CSA) is the 20th largest in the United States.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 the 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. Designated as a global city by the Globalization and World Cities Research Network, the GDP of Greater St. Louis was $187.6 billion in 2021. St. Louis has a diverse economy with strengths in the service, manufacturing, trade, transportation, and aviation industries. It is home to fifteen Fortune 1000 companies, seven of which are also Fortune 500 companies. Federal agencies headquartered in the city or with significant operations there include the Federal Reserve Bank of St. Louis, the U.S. Department of Agriculture, and the National Geospatial-Intelligence Agency. Major research universities in Greater St. Louis include Washington University in St. Louis, Saint Louis University, and the 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.