Cahokia Mounds

Cahokia Mounds occupies a site in southwestern Illinois directly across the Mississippi River from modern St Louis, the largest and most influential urban settlement built by the Mississippian culture, flourishing roughly between 1050 and 1350 AD. Of an estimated 120 earthen mounds raised at the city's height, about 80 survive within the modern archaeological park, dominated by Monks Mound, a massive platform structure rising some 100 feet with a footprint of 951 by 836 feet, covering nearly 14 acres and ranking among the largest pre-Columbian earthworks north of Mexico. At its peak around 1100 AD the city is estimated to have held between 15,000 and 20,000 residents, with some scholars suggesting the true figure may have reached as high as 40,000, a scale that made Cahokia one of the largest cities anywhere in the world at that time. UNESCO designated the site a World Heritage Site in 1982, and it remains the only such self-contained designation in Illinois.