The text surveys prehistoric earthen mounds across the Mississippi Valley and neighboring regions, describing their shapes, contents, and likely functions—effigy figures, temple platforms, and burial or sacrificial tumuli—and highlights major complexes including a large serpent effigy. It examines skeletal and linguistic evidence used to propose origins, outlines cephalic classifications and migration hypotheses from the Caribbean and Bering Strait, and notes a distinctive craniological type in Midwestern collections. Comparative craniology and philology are presented as the principal tools for evaluating competing theories while recording regional mound forms and distributions.