Cahokia is a settlement and former village in St. Clair County, Illinois, United States, founded as a colonial French mission in 1689. Located on the east side of the Mississippi River in the Greater St. Louis metropolitan area, as of the 2010 census, 15,241 people lived in the village. On May 6, 2021, the village was incorporated into the new city of Cahokia Heights. The name refers to one of the clans of the historic Illiniwek confederacy, who met early French explorers to the region.