When U.S. 40 reaches Collinsville, Illinois, the land is flat and open. Seedy storefronts line the highway: a pawnshop, a discount carpet warehouse, a taco joint, a bar. Only the Indian Mound Motel gives any hint that the road bisects something more than underdeveloped farmland.
This is the Cahokia Mounds State Historic Site, a United Nations World Heritage Site on a par with the Great Wall of China, the Egyptian pyramids, and the Taj Mahal.
The 4,000-acre complex preserves the remnants of the largest prehistoric settlement north of Mexico, a walled city that flourished on the floodplain of the Mississippi River 10 centuries ago.
Covering an area more than five miles square, Cahokia dwarfs the ancient pueblos of New Mexico’s Chaco Canyon and every other ruin left by the storied Anasazi of the American Southwest. Yet despite its size and importance, archaeologists still don’t understand how this vast, lost culture began, how it ended, and what went on in between.
A thousand years ago, no one could have missed Cahokia—a complex, sophisticated society with an urban center, satellite villages, and as many as 50,000 people in all.
Thatched-roof houses lined the central plazas. Merchants swapped copper, mica, and seashells from as far away as the Great Lakes and the Gulf of Mexico. Thousands of cooking fires burned night and day.
And between A.D. 1000 and 1300, Cahokians built more than 120 earthen mounds as landmarks, tombs, and ceremonial platforms. The largest of these monuments, now called Monks Mound, still dominates the site. It is a flat-topped pyramid of dirt that covers more than 14 acres and once supported a 5,000-square-foot temple.
Monks Mound is bigger than any of the three great pyramids at Giza outside Cairo. “This is the third or fourth biggest pyramid in the world, in terms of volume,” says archaeologist Tim Pauketat of the University of Illinois at Urbana-Champaign.
It towers 100 feet over a 40-acre plaza that was surrounded by lesser mounds and a two-mile-long stockade. The monument was the crowning achievement of a mound-building culture that began thousands of years earlier and was never duplicated on this continent.