 Over the course of its excavation between 1969 and 1978, Koster produced deeply buried evidence of ancient human occupation from the early Archaic period (BC 7500) to the Mississippian period (AD 1000).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.