Who were the Adena Mound Builders of North America?

The Adena tradition was an Early Eastern Woodland Native American culture that existed from about 1000 to 200 B.C.E. The Adena were not a single tribe but rather a conglomerate of Northeastern American peoples who shared various cultural characteristics, such as a common burial and ceremonial system. They are mostly known for their erection of beautiful earthen burial mounds. The Adena are perceived by archaeologists as being the progenitor of the more elaborate Hopewell tradition, which rose to prominence directly after the Adena faded into obscurity in the third century B.C.E.

Sources:
Albert C. Spaulding (1952). "The Origin of the Adena Culture of the Ohio Valley," Southwestern Journal of Anthropology 8, no. 3. 260-268. https://doi.org/10.1086/soutjanth.8.3...

Adena Culture. (n.d.). Retrieved from http://ohiohistorycentral.org/w/Adena...

Henderson, A. G. (2007). Adena: "Woodland period moundbuilders of the Bluegrass". Lexington, KY: Kentucky Heritage Council. 3-50

Webb, W. S., & Snow, C. E. (2001). "The Adena people". Knoxville: University of Tennessee Press. 110-132