The Cahokia site covers 2, 200 acres. Within this area lie the archaeological remnants of the ancient city. The site contained 120 large earthen mounds. Monks Mound is by far the largest. There were three types of mounds. Flat topped pyramid shaped mounds served as bases for houses for chiefs and high ranking persons or as elevated bases for temples. Conical mounds were used for burial of important people. Ridgetop mounds marked impotent locations.
The city of Cahokia was surrounded by a 400 yard palisade which featured bastions, or watch towers. Several large circles of posts called "Woodhenges" were used as astronomical calendars. Cahokia controlled a large suburban and rural network throughout southwestern Illinois until it's decline in 1400 A.D. It had influences as far away as Wisconsin, Georgia, and Oklahoma.
Cahokia is the largest urban center of prehistoric time in the New World, north of Mexico. Populations estimates range from a low of 5,000 to a high of 40,000. The political leader lived on top of Monks Mound, possibly in the remains of a structure measuring 150 feet by 50 feet found on the uppermost or fourth terrace. Remains of other structures have been found on the lower three terraces.
In front of Monks Mound was a large plaza area where religious ceremonies and public gatherings took place. The plaza area was surrounded by the palisade. The palisade is thought to have served as a social barrier rather than a defensive barrier. Those who lived inside the palisades, particularly the chief seem to carry enormous political and economic power. One of the people buried in Mound 72 had a number of craft specialists buried with him as well as two rolls of sheet copper, 800 arrowheads, and a basketload of mica. Also buried with him were 53 women ages 15 to 25.
Despite the good food, high social organizations people lived short lives. A Mississippian who lived to 21 could expect tolive another 17. Unlike their ancestors, the indians at Cahokia were troubled with high tooth decay. Higher carbohydrates associated with corn horticulture was probably the main cause. Crowded urban lifestly brought on communicalbe diseases, one of the worst of which was tuberculosis.
Cahokia was abandoned by 1400 A.D. No single cause can account for the abandonment. Possible explanations include warfare, disase, weather changes creating economic problems and maybe the people just overused and destroyed the environment on which they depended. Some combination of these reasons probably explains the extinction of this complext prehistoric society.