Between 900-1050 A.D, Native American Indians known as Mound Builders built a town center with four mounds, a town square, individual dwellings, and a separate cemetery area, along with a fifth mound outside the town center overlooking the Little Harpeth River. The tallest, Mound #1, rose 25 feet on a 6 foot natural knoll from soil removed from the square and Mound #4 and probably held the tribal leader's house. On the west side of the square, Mound #2 began as a dwelling area, then was repeatedly covered with soil, rebuilt, and raised again after homes were destroyed and a tribal ceremonial house was later burned, though its final evidence was lost to farm cultivation. On the southwest corner of the square, Mound #3 was a flexed-burial mound built atop a natural knoll and raised as bodies were buried, and it probably contained 15 stone-slab graves from a later group. Mound #4 was a low, four-foot mound formed by the removal of soil used for Mound #1 and may have supported an important building, though erosion and cultivation destroyed evidence of its use. Mound #5 was a small three-foot oval mound overlooking the river that contained a domestic fire bed. The Mound Builders, part of the golden era of the Mississippian period, lived in permanent planned ceremonial centers and large towns surrounded by smaller towns and villages, relied primarily on agriculture, and took part in complex social, religious, and political systems. By the 1500s, they and their culture had mysteriously disappeared, and they were the last prehistoric Native Americans to live in this area. In 1920, archaeological research found artifacts including arrowheads, pottery, tools, and grave items from Mound #3, and all were sent to the Smithsonian.