The Poverty Point culture was a prehistoric Native American culture that flourished in the lower Mississippi River Valley from 1700 to 1100 BCE. This culture is best known for its large earthworks, which were constructed in the form of concentric circles, ridges, and mounds. These earthworks were used
From Wikipedia
Poverty Point State Historic Site/Poverty Point National Monument is a prehistoric earthwork constructed by the Poverty Point culture, located in present-day northeastern Louisiana. Evidence of the Poverty Point culture extends throughout much of the Southeastern Woodlands of the Southern United States. The culture extended 100 miles (160 km) across the Mississippi Delta and south to the Gulf Coast.