They retrace their footsteps many times. Days pass, and as the ribbon of workers relentlessly empties baskets, a shape emerges and grows to great height. Variations of this scene were repeated for some 5,500 years throughout the rich bottomlands of the Lower Mississippi Valley. The shapes of mounds vary. They can be flat topped pyramids, cones, ovals, or barely perceptible rises on the landscape.
Mounds can stand alone or be in clusters of as many as twenty constructions.
Some mounds are clustered around broad plazas, while others are connected by earthwork ridges. Signs of stockades and ditch fortifications enclosing some mounds imply warfare. The lack of discernible defenses at other sites suggest peaceful periods. How Native Americans used the mounds also varied. The purposes of some of the most ancient mounds are still shrouded in mystery.