Mounds are greatly scattered, found as far north as Aztalan (WI), as far south as Davis (TX) and east of both. Their purposes are as mysterious as their builders. They were anywhere from very small to as large as Monks Mound at Cahokia (IL). It is 100 feet high, covers 16 acres and contains almost 22 million cubic feet of earth. Most mounds were flat-topped or pyramidal in shape. Some were used to make large enclosures but others took animal shapes such as the Serpent Mounds in southern Ohio. Many were burial mounds, sometimes containing one grave with elaborate grave goods, sometimes many graves. Other mounds were believed to be temple mounds, perhaps used just once a year for ceremonial purposes or competitions. Usually found on or near the mounds were carefully cleared areas of ground called Chunkey yards. Chunkey was a popular disc game of the time.
Among the many exquisite items that have been excavated from some mound sites, the finest surviving "graphic" art is that inscribed on shell. The most frequent shell form is the shell gorget, a flat piece of shell generally circular in shape. The tops were perforated by two holes through which a leather thong was inserted so it could be worn around the neck.