From the record
“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.”
Wikipedia article Koster Site, CC BY-SA 4.0.
One of 12 National Register listings published here for Greene County · listed in 1972 · category: Site.
Sources: the Wikipedia article · the National Register database, National Park Service
