Prehistory

Main article: Mississippian culture

Among the American Indians Paleoindian cultures were the earliest in North America, with a presence in the Great Plains and Great Lakes areas from about 12,000 BCE to around 8,000 BCE.^{[citation needed]}

Monks Mound, located at the Cahokia Mounds near Collinsville, Illinois, is the largest Pre-Columbian earthwork in America north of Mesoamerica.

Following the Paleo-Indian period is the Archaic period (8,000 BCE to 1,000 BCE), the Woodland Tradition (1,000 BCE to 100 CE), and the Mississippian Period (900 to 1500 CE). Archaeological evidence indicates that Mississippian culture traits probably began in the St. Louis, Missouri area and spread northwest along the Mississippi and Illinois rivers and entered the state along the Kankakee River system. It also spread northward into Indiana along the Wabash, Tippecanoe, and White Rivers.^[15]
Mississippian peoples in the Midwest were mostly farmers who followed the rich, flat floodplains of Midwestern rivers. They brought with them a well-developed agricultural complex based on three major crops—maize, beans, and squash. Maize, or corn, was the primary crop of Mississippian farmers. They gathered a wide variety of seeds, nuts, and berries, and fished and hunted for fowl to supplement their diets. With such an intensive form of agriculture, this culture supported large populations.^{[citation needed]}
The Mississippi period was characterized by a mound-building culture. The Mississippians suffered a tremendous population decline about 1400, coinciding with the global climate change of the Little Ice Age. Their culture effectively ended before 1492.^[16]