Cahokia

Cahokia was located in the American Bottom, a fertile floodplain near the confluence of the Mississippi, Missouri and Illinois river systems. It grew during the Mississippian period, with its most intensive occupation generally dated from about 800 to 1400. By around 1050–1150, the settlement and its surrounding communities formed a complex regional centre. Archaeologists distinguish the central settlement from a wider network of related sites and villages.

Cahokia's landscape included platform, ridgetop and conical mounds, as well as plazas, houses, public structures and activity areas. Monks Mound, built in stages and arranged in terraces, is the largest prehistoric earthen structure in the Americas. Archaeological evidence indicates that mounds served different purposes, including as foundations for important buildings and, in some cases, as burial places. A reconstructed palisade and the post circle known as Woodhenge help illustrate aspects of the site's organization and ceremonial life.

Cahokia was an agricultural society whose population supported specialists, public construction and regional exchange. UNESCO describes it as an example of a complex chiefdom society with satellite mound centres and outlying hamlets and villages. Estimates for the population at its peak vary; UNESCO gives a range of 10,000 to 20,000 for the central society, while the National Park Service notes that estimates for a wider Greater Cahokia region have been higher. These numbers are estimates rather than a census.

The site provides evidence of large-scale Indigenous planning, earthwork construction and social organization before sustained European contact. Cahokia Mounds State Historic Site preserves the central portion of the archaeological landscape, while research continues on the site's chronology, environment, political organization and connections with other Mississippian communities. Interpretation should recognize that Cahokia was created by Indigenous peoples and that descendant and affiliated communities remain connected to the site's heritage.

The State of Illinois protects the central historic site. Cahokia was designated a U.S. National Historic Landmark in 1965 and was inscribed on the UNESCO World Heritage List in 1982. UNESCO identifies threats including erosion, development, flooding and damage to subsurface archaeological features. Conservation therefore combines legal protection, site management, research and public interpretation.