The statements that are true about the Caddoan Mound Builders are:
>They were likely a part of the Mississippian culture.
>They built earthen mounds to use exclusively as burial sites.
The culture of the mounds is a pre-Columbian archaeological culture that developed in the south and southeast of the current United States. Mound builders were the carriers of this culture, which probably belonged to different ethnic and linguistic groups. The highest concentrations of burial mounds are in the state of Ohio, where more than 10,000 have been located. One of the most representative sites of mound cultures is Cahokia, in the Mississippi Valley.
These pre-Columbian cultures lived during the archaic period, the silvicultural period that included the Hopewell and Adena cultures and finally, the era of the Mississippi culture, already in the centuries and years prior to the arrival of the Europeans to the American continent. All this, in chronological terms, from about 3000 BC to the sixteenth century.