Koster Site

The Koster Site is a prehistoric archaeological site located south of Eldred, Illinois. The site covers more than 3 acres and extends 30 feet down into the alluvial deposits of the Illinois River valley. Over the course of its excavation between 1969 and 1978, Koster produced deeply buried evidence of ancient human occupation from the early Archaic period to the Mississippian period. The soil strata contains a total of 25 distinct occupations each separated by additional layers of soil, making the site exceptionally well-preserved.

The site includes one of the oldest known cemetery sites in eastern North America. The cemetery site has provided researchers with evidence that Early Archaic civilizations had specific burial practices and buried their dead in mounds, often with numerous individuals buried together.