Answer: The "Mound Builder" cultures span the period of roughly 3500 BCE (the construction of Watson Brake) to the 16th century CE, including the Archaic period, Woodland period (Calusa culture, Adena and Hopewell cultures), and Mississippian period. Geographically, the cultures were present in the region of the Great Lakes, the Ohio River Valley, and the Mississippi River valley and its tributary waters. The Cahokia Mounds State Historic Site is the site of a pre-Columbian Native American city (which existed c. 1050–1350 CE) directly across the Mississippi River from modern St. Louis, Missouri. This historic park lies in south-western Illinois between East St. Louis and Collinsville.
