East Saint Louis (lōˈĭs) [key], city (1990 pop. 40,944), St. Clair co., SW Ill., on the Mississippi River opposite St. Louis; inc. 1859. Once a rail and transportation hub with stockyards and warehouses, East St. Louis has suffered serious economic decline; in 1994 Illinois took over operation of the city government. Oil refining, steel, chemicals, glass, and construction materials have all been important industries, but unemployment, population loss, and social problems have wracked the city since the 1960s. A riverboat gambling casino is now a major employer.
The city was once the site of significant Native American mounds built during the Mississippian period (see Mound Builders), but they were leveled as the city grew. The first European settlement here was in 1765. Cahokia Creek was bridged in 1795, and a ferry across the Mississippi began operation shortly thereafter. East St. Louis was plagued by devastating floods until its first dike was completed in 1909. Just northeast are the Cahokia Mounds.