Mound Builders, in North American prehistory, was the designation granted to those people who raised mounds in a large field from the Mississippi River to the Appalachian Mts and Great Lakes to the Gulf of Mexico. The most prominent congregations of mounds are recognized in the Ohio plains. The hills matched 65 ft. in height and were fashioned solely by standard labor. Mound builders existed in dome-shaped houses constructed with pole walls and thatched rooftops.