The Cahokia Mounds State Historic Site (11 MS 2) is located on the site of a pre-Columbian Native American city ( 600–1400 AD) situated directly across the Mississippi River from modern St. Louis, Missouri. This historic park lies in southern Illinois between East St. Louis and Collinsville. The park covers , or about , and contains about 80 mounds, but the ancient city was much larger. In its heyday, Cahokia covered about and included about 120 human-made earthen mounds in a wide range of sizes, shapes, and functions.