Cahokia Mounds. From Alcott1

RR Just Viewcards. Group 72 

Cahokia Mounds State Historic Site is the area of an ancient indigenous citynear Collinsville, Illinois.
It is a National Historic Landmark and designated site for state protection. In addition, it is one of only twenty one World Heritage Sites in the territory of the United States. It is the largest prehistoric earthen construction in the Americas north of Mexico.