Cahokia Mounds, The Largest Pre-Columbia Earthen Human Settlement in the New World

I recently revisited Cahokia Mounds Historical Site in Collinsville, MO, just a few miles outside of St. Louis, in September, 2012.

Cahokia Mounds is remarkable not only because it is the largest pre-Columbian earthen set of human-built structures, not only because much has been learned about this previous little known Mississippian culture, but also because it is so little known to most of the world. Outside of a small number of Lewis and Clark buffs, of archeologists specializing in Mississippian cultures, and outside of people who live near the site, Cahokia seems unknown. At least none of my friends or colleagues know about it until I tell them or they read my book, Beyond The Stony Mountains, which discusses William Clark's first encounter with the Cahokia Mounds in 1804.

A wonderful amount of new information had been discovered by archeologists about Cahokia’s ancient culture since my previous visit there more than a decade before, and a beautiful and highly educational museum had developed, well worth a visit. Several major mounds were now accessible by walking paths. A reconstruction of “Woodhenge” a circle of tree stakes around a central stake, had been built following what is known about the ancient construction methods. Like Stonehenge, Woodhenge marked the spring and summer equinox, thereby providing a guide to the seasons.

If you ever get to or near St. Louis, Missouri, don’t miss a chance to go to Cahokia. For more information about visiting Cahokia Mounds, go to www.cahokiamounds.org or @CahokiaMounds on Twitter.

Here is an excerpt about the Cahokia Mounds from Beyond The Stony Mountains, now available as an ebook for the first time.

William Clark and Cahokia Mounds

On Monday, January 9, 1804, William Clark, an outdoorsman, took time off from paperwork and other responsibilities (in preparing for his and Meriwether Lewis’s expedition across the American West) and, enlisting John Collins, one of the men he had hired for the expedition, "went across a Prary to a 2nd Bank." There he came to a curious place. "I discovered an Indian Fortification," he wrote. Confronted with something new, Clark responded by taking measurements—a habit that would be his characteristic throughout the journey. "9 mouns forming a Circle," he recorded. "[The base of] two of them is about 7 foot above the leavel of the plain on the edge of the first bank and 2 m from the woods," he continued. Looking around the mounds, he found "great quantities of Earthen ware & flints" and a "Grave on an Emenince."

The mounds were not in use. They were ancient and abandoned. The local Indians knew little about them. He had unwittingly stumbled onto what we now call Cahokia Mounds, the remains of the largest prehistoric earthen construction in the New World, built, according to discoveries by modern archeologists, between AD 700 and AD 1400. Looking back from our perspective, it was an ironic and curious discovery. He and Lewis were about to embark on a journey into what was perceived to be wilderness conforming to a formal set of European beliefs about nature in the New World, and Clark finds, quite accidentally and without any guidance, evidence that they were in the backyard of Native Americans who had affected that countryside much longer than anyone understood.

This suggested very different connections between people and nature than would be assumed from the European belief that this was "virgin territory." It demonstrated unequivocally that the lands along the Missouri River had long been settled by Native Americans who had carefully selected where to live in regard to nature's resources and who had had lasting effects on the countryside. Observing the connections between ancient peoples of North America and their environment, Clark found himself in a countryside that did not meet classical European assumptions about nature every where—something he and Lewis would soon discover wherever they went.

And just as the foundation of the largest mounds formed a base for others, the Indian cultures would provide a foundation for the expedition. The help that the Indians would give to the Corps of Discovery during their trip would be invaluable. It is fair to say that the expedition would not have succeeded without that help. Today the mounds are preserved as the Cahokia Mounds State Historic Site. They form the largest prehistoric city in the New World north of Mexico. Approaching from St. Louis, entering the town of Collinsville, Illinois, one sees a tall mound rising surprisingly high above the level farmland, back behind fences in a large open field. Archeological studies indicate that, at its peak, the great mound city held about twenty thousand inhabitants, an urban population density similar to that of modern St. Louis.

It is no accident that an ancient urban concentration and the modern city of St. Louis arose in the same area, because the environment near the confluence of the Missouri and Mississippi rivers offers many benefits. Just east of the confluence, the broad, flat floodplain offered good land for farming and habitat that attracted wildlife, drawn by the water and the vegetation that grew along the rivers. Rivers were then and remain important for transportation. And it is pleasant to be near a river.

The interactions and relationships between people and nature interested Clark, who, throughout the journey, looked at the countryside and envisioned future cities, towns, farms, forts, and harbors. And here he was, before the journey began, looking at Cahokia. The great mound city had been surrounded by a two-mile-long stockade of logs twenty feet high built from about twenty thousand trees. At the height of its development, Cahokia included 120 mounds, all of earth. A large ceremonial mound reached one hundred feet high, with a base of fourteen acres and a building on top more than one hundred feet long and forty-eight feet wide, and another mound was fifty feet high. More than fifty million cubic feet of earth were moved for the construction of the mounds.

The sophistication of the culture that developed here was revealed by archeological excavation in the 19605 that was spurred by a plan to put an interstate highway through the location. An archeologist, Warren Wittry, discovered oval-shaped pits the size of posts made from trees and arranged in arcs of circles. These appear to have served as celestial calendars, much as Stonehenge did in England, and have become known as Woodhenge. The posts mark the winter and summer solstices and spring and fall equinoxes.

Like other early agricultural people, the Cahokians were dependent on the seasons for planting and harvest and needed a method to predict when changes would come. A densely populated, defended city was possible here near the confluence of the Missouri and Mississippi rivers because the rivers and the surrounding countryside provided abundant natural resources. The floodplain's soil was frequently reenriched when the rivers flooded and deposited new soil carried from far upstream. Fish, freshwater shellfish, migrating and nesting water birds, and native mammals, including deer, were abundant in the complex habitats along the river and over the wide floodplain.

The location of the largest prehistoric city in North America was not accidental but a direct result of geography. Living close to the land and depending on it, the people of Cahokia responded to local differences in their natural resources. They farmed along the eastern floodplain of the Mississippi, but not along the western shore.

At the time, the western shore was a series of bluffs and valleys, comparatively poor land to farm. Today, you would not notice this difference because the bluffs have been removed and the land leveled as part of the development of St. Louis.

The city of Cahokia began a gradual decline around AD 1300 and was abandoned by AD 1500. Nobody knows the fate of its people. The Indians Clark met near St. Louis knew no more than he did about the mounds. The history of the greatest city of ancient times in North America had been lost. Did the mound builders overuse their natural resources and then die off or migrate away because they had destroyed their local environment? Did a change of climate around AD 1400 make it impossible for them to live? (The decline coincided with the end of the Medieval Warming and the beginning of The Little Ice Age, both of which affected North America.) Or did politics and war put an end to their culture? Nobody knows. Bones of the dead suggest some malnutrition and disease, so perhaps there was an environment-related decline in this civilization. Perhaps it is a history lesson we should pursue to see if there is any warning or message to help our civilization sustain itself and also sustain its natural resources.

Except from Beyond the Stony Mountains: Nature in the American West from Lewis and Clark to Today, chapter 1, Botkin, D. B. 2012. Copyright © 2012 Daniel B. Botkin. All Rights Reserved. Do not copy, circulate or publish elsewhere without the author’s permission.