1. Cahokia Mounds (Illinois)
Just outside modern St. Louis lies Cahokia Mounds, the epicenter of a thriving city that peaked around 1200 CE. This remarkable site, recognized as a UNESCO World Heritage treasure, preserves over 80 mounds crafted by the Mississippian culture. The largest, Monk’s Mound, soars above the landscape as the biggest earthen structure in the Western Hemisphere. Visitors today can wander these ancient grounds and imagine a bustling metropolis that once rivaled the great cities of its era. For more details, visit the National Park Service.
