What was the social structure of the mound builders?

Answer 1

They were a chiefdom with a ruling class and a common class. The mounds were topped by temples and residences of the ruling class. Upon the death of a ruler, the residence would be burned as a cleansing and afterwards the deceased would be buried in a new layer of clay atop the previous mound.

Answer 2

There wasn't much of a social class ranking. They were pretty good with each other with the help of the chief.