Pre-European

Mississippian copper plate found at the Saddle Site in Union County, Illinois
American Indians of successive cultures lived along the waterways of the Illinois area for thousands of years before the arrival of Europeans. The Koster Site has been excavated and demonstrates 7,000 years of continuous habitation. Cahokia, the largest regional chiefdom and Urban Center of the Pre-Columbian Mississippian culture, was located near present-day Collinsville, Illinois. They built an urban complex of more than 100 platform and burial mounds, a 50-acre (20 ha) plaza larger than 35 football fields, and a woodhenge of sacred cedar, all in a planned design expressing the culture’s cosmology. Monks Mound, the center of the site, is the largest Pre-Columbian structure north of the Valley of Mexico. It is 100 ft (30 m) high, 951 ft (290 m) long, 836 ft (255 m) wide, and covers 13.8 acres (5.6 ha). It contains about 814,000 cu yd (622,000 m3) of earth. It was topped by a structure thought to have measured about 105 ft (32 m) in length and 48 ft (15 m) in width, covered an area 5,000 sq ft (460 m2), and been as much as 50 ft (15 m) high, making its peak 150 ft (46 m) above the level of the plaza. The finely crafted ornaments and tools recovered by archaeologists at Cahokia include elaborate ceramics, finely sculptured stonework, carefully embossed and engraved copper and mica sheets, and one funeral blanket for an important chief fashioned from 20,000 shell beads. These artifacts indicate that Cahokia was truly an urban center, with clustered housing, markets, and specialists in toolmaking, hide dressing, potting, jewelry making, shell engraving, weaving and salt making.

The civilization vanished in the 15th century for unknown reasons, but historians and archeologists have speculated that the people depleted the area of resources. Many indigenous tribes engaged in constant warfare. According to Suzanne Austin Alchon, “At one site in the central Illinois River valley, one third of all adults died as a result of violent injuries.” The next major power in the region was the Illinois Confederation or Illini, a political alliance. As the Illini declined during the Beaver Wars era, members of the Algonquian-speaking Potawatomi, Miami, Sauk, and other tribes including the Fox (Meskwaki), Iowa, Kickapoo, Mascouten, Piankeshaw, Shawnee, Wea, and Winnebago (Ho-Chunk) came into the area from the east and north around the Great Lakes.