St. Louis is an independent city and a major U.S. port in the state of Missouri, built along the western bank of the Mississippi River, which marks Missouri’s border with Illinois. The city had an estimated 2017 population of 308,626[8] and is the cultural and economic center of the St. Louis metropolitan area (home to nearly 3,000,000 people), which is the largest metropolitan area in Missouri, the second-largest in Illinois (after Chicago), and the 22nd-largest in the United States.St. Louis, Missouri | Missouri Flag | IASTL