St. Louis /seɪnt ˈluːɪs/ (French: Saint-Louis or St-Louis, ) is an independent city on the eastern border of Missouri, United States, and it is the second-largest city in the state. With a population of 318,069 in July 2011, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St. Louis combined statistical area (CSA) population of 2,882,932 is the 15th-largest in the country and is the largest in Missouri.
The city of St. Louis was founded in 1764 by Pierre Laclède and Auguste Chouteau, and after the Louisiana Purchase, it became a major port on the Mississippi River. Its population expanded after the American Civil War, and it became the fourth-largest city in the United States in the late 19th century. It seceded from St. Louis County in March 1877, allowing it to become an independent city and limiting its political boundaries. In 1904, it hosted the 1904 World's Fair and the 1904 Olympic Games. The city's population peaked in 1950, then began a long decline that continues in the 21st century.
The economy of St. Louis relies on service, manufacturing, trade, transportation of goods, and tourism. The region is home to several major corporations: Express Scripts, Enterprise Rent-A-Car, Graybar Electric, Scottrade, Sigma-Aldrich, Anheuser-Busch, Edward Jones Investments, Emerson Electric, Energizer, and Monsanto. St. Louis is home to three professional sports teams: the St. Louis Cardinals, one of the most successful Major League Baseball clubs; the hockey St. Louis Blues, and the football St. Louis Rams. The city is commonly identified with the Gateway Arch, part of the Jefferson National Expansion Memorial in downtown St. Louis.