Cahokia is the site of an ancient indigenous city (650–1400 CE) near Collinsville, Illinois. In the American Bottom floodplain, it's across the Mississippi River from St. Louis, Missouri. The site included 120 man-made earthen mounds over an area of six square miles, although only 80 survive. "Cahokia Mounds State Historic Site, Illinois", US World Heritage Sites, National Park Service, accessed 13 May 2009 Cahokia Mounds is the largest archaeological site related to the Mississippian cul… (More on Cahokia)