St. Louis French: Saint-Louis or St-Louis, is an independent city and the second largest city in the U.S. state of Missouri. The city has an estimated population of 356,587 and is the principal municipality of Greater St. Louis, population 2,892,874, the largest urban area in Missouri and 15th-largest in the United States. St. Louis was founded in 1764 just south of the confluence of the Missouri and Mississippi rivers in what is today the Midwestern United States by colonial French traders Pierre LaclÃ¨de and RenÃ© Auguste Chouteau, who named the settlement after King Louis IX of France. The early wealth of the city was based on the fur trade. The city, as well as the future state of Missouri, became part of the Spanish Empire after the French were defeated in the Seven Years’ War.