From Ohio History Central
Miamisburg Mound is one of the two largest conical mounds in eastern North America. The other is West Virginia's Grave Creek Mound. It is a burial mound built by the people that archaeologists have called the Adena culture (800 B.C. to 100 A.D.). Adena was the name Governor Thomas Worthington called his estate in Chillicothe, Ohio. It was at that estate that the first mound of this group of prehistoric Native Americans was excavated in 1901.
The Miamisburg Mound is 65 feet tall and 800 feet in circumference. It contains 54,000 cubic yards of earth, which corresponds to the contents of more than 3,400 dump trucks.