A Native American city near St. Louis once outgrew medieval London

Around 1050 AD, the Mississippian city of Cahokia held roughly 10,000 to 20,000 residents across 120-plus earthen mounds, making it larger than London at the time. Its largest structure, Monks Mound, covers more ground at its base than the Great Pyramid of Giza. By 1350 the city was abandoned, and archaeologists still debate why.

— Timothy R. Pauketat, Cahokia: Ancient America's Great City on the Mississippi — Viking, 2009
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