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.
Why Cahokia crumbled and its people vanished is unknown. Malnutrition, overcrowding, a dwindling resource base, the raids of jealous trade partners—any or all of these reasons may have contributed to the city’s demise. No one knows whether the populace cleared out all at once or dispersed gradually, but by A.D. 1300 Cahokia was a ghost town. By the time Europeans arrived in the Mississippi bottomland, the region was only sparsely settled, and none of the native residents could recount what had happened there centuries before.
So far, archaeologists have uncovered no evidence of invasion, rampant disease, overpopulation, deforestation, or any of the other hallmarks of the decline and fall of civilization. Cahokia abounds in artifacts, but archaeologists have not yet made sense of them in a meaningful way. “It actually becomes quite scary,” says John Kelly of Washington University in St. Louis. “After a while you begin to realize that you’re dealing with rituals that had a great deal of meaning 800 years ago and that you’re kind of clueless.”
Intellectual frustration is not the only reason for Cahokia’s obscurity. Pauketat complains that the region is geographically challenged. It has the look and feel of a place “like Buffalo, except warmer,” he says. Cahokia doesn’t exactly lure others away from more exotic digs in Turkey, Mexico, or Peru, he says. “That’s the problem with this site.” Another reason for its lack of popularity is the ordinary, perishable building materials used by the residents. “Cahokians are discounted because they built with dirt—dirt and wood, things they valued,” says Pauketat. “I get tired of hearing people say, ‘We have civilization and you guys don’t.’ ”
Meanwhile, developers see Cahokia as ripe for expansion; strip malls and subdivisions threaten on every side. “It’s developing faster than we can survey,” Pauketat says. “We don’t know what we’re losing out there.” Although a good portion of the central city is now protected, archaeologists are discovering related sites throughout a six-county region on both sides of the nearby Mississippi—an area 3,600 miles square. Indeed, digs are under way in such unlikely places as a railroad yard eight miles west in East St. Louis, where a new bridge is scheduled. “If you want to find out the archaeology of an area,” says Brad Koldehoff of the Illinois Department of Transportation’s archaeology team, “build a road through it.”