Monks Mound

Start with the grass under your feet. It is soft, a little springy, and it rises steadily ahead of you. This is not a natural hill. Every bit of the slope in front of you was carried here by human hands, one load of soil at a time. On a quiet morning you can hear wind moving across the open fields and the faint hum of traffic in the distance. Then you look up, and the scale of what people built here begins to settle in.

You are standing at Monks Mound, the largest prehistoric earthen structure in the Americas. It sits at the heart of Cahokia Mounds State Historic Site, in Illinois, just across the Mississippi River from Saint Louis. The mound rises roughly thirty metres above the floodplain. Its base covers about fourteen acres, which is a larger footprint than the Great Pyramid of Giza. It was not built of stone. It was built of earth, and that makes the achievement even more remarkable.

The people who built it belonged to what archaeologists call the Mississippian culture. This was a farming society that grew maize, squash, and other crops in the rich soils along the great rivers of the American Midwest and South. We do not know what they called themselves, or what they called this place. The name Cahokia comes from a later group of Native people who lived in the area when French explorers arrived. The builders themselves left no written records, so much of what we know comes from careful excavation.

Construction happened in stages, beginning around the tenth century and continuing for roughly two to three hundred years. Workers dug soil from nearby pits, which archaeologists call borrow pits, and carried it in baskets on their backs. Different layers used different kinds of soil — sandy earth, dark clay, lighter silt. Some researchers think the builders mixed these materials on purpose to help the mound drain water and hold its shape. Estimates suggest millions of baskets of earth went into the finished structure.

Here is something many visitors miss. Monks Mound is not a single smooth hill. It was built as a series of flat terraces, stacked one above another. The lowest terrace faces south, toward the open ground in front of you. From the ground the shape can look softened and rounded, because centuries of rain have worn the edges. But if you walk around the base, you can still see how the levels step upward toward the summit.

On the very top, excavations found the traces of a very large building. Its walls were made of wooden posts, and only the dark stains of those post holes survive in the soil. Most archaeologists believe this was a residence or temple for Cahokia's most powerful leader. From up there, a ruler could look out across the whole city. And it was a city. At its height, around the eleventh and twelfth centuries, Cahokia may have been home to somewhere between ten and twenty thousand people.

To put that in perspective, that population was comparable to many European cities of the same era. For centuries afterward, no settlement north of Mexico grew larger. When the United States took its first census, Saint Louis and Philadelphia were still smaller than Cahokia had once been. Yet for a long time, many Americans refused to believe that Native people had built these mounds at all. Those false theories are now firmly rejected. The evidence in the soil is clear.

Look south from the base of the mound, and you will see a wide, flat, grassy space. This was the Grand Plaza. Builders levelled and filled it deliberately, creating a huge public open space. Archaeologists think people gathered here for ceremonies, markets, and games. One game, called chunkey, involved rolling a stone disc across the ground while players threw long sticks toward where they expected it to stop. Stone chunkey discs have been found across the Mississippian world.

The central part of the city, including the mound and the plaza, was at one time surrounded by a tall wall of upright logs. This wall, called a palisade, was rebuilt several times. Archaeologists can trace its line through rows of post holes in the ground. Nobody is certain whether it was built mainly for defence, or to separate the elite centre from the rest of the city. Perhaps it did both. Today, a short reconstructed section helps visitors picture its height.

The name Monks Mound is much more recent. In the early nineteenth century, a small community of French Trappist monks settled nearby. Trappists are a strict Catholic religious order known for prayer, silence, and farming. The monks grew vegetables on the terraces of the mound. Their stay was short, but their name remained attached to it. It is a strange twist of history — a structure built by Mississippian people, named for European monks who lived here only briefly.

Across the river, Saint Louis has its own story with mounds. The city once had so many that it carried the nickname Mound City. Almost all of those mounds were levelled in the nineteenth century as the city expanded, including one called Big Mound. Monks Mound survived partly because it stood on the other side of the river, on farmland. Today it is part of a UNESCO World Heritage Site, protected as one of the most important places in North American history.

The mound is not frozen in time. Earth moves. Over the years, heavy rains have caused parts of the slopes to slump and slide. Engineers and archaeologists have worked to stabilise these areas, and you may notice places where the surface looks repaired. That is also why visitors are asked to stay on the staircase and the marked paths. Every footstep off the path wears away soil that took human hands generations to place.

If you climb the stairs to the summit, take your time. The view rewards you. On a clear day, you can see the towers of downtown Saint Louis and the curve of the Gateway Arch on the western horizon. Between here and there lies the wide floodplain that once fed this city. Imagine smoke from cooking fires, the sound of voices, the thatched roofs of houses spreading out below you in every direction.

Cahokia's population declined over time, and by around 1400 the city was largely empty. Archaeologists still debate why. Possible reasons include climate change, flooding, political conflict, and the strain of feeding so many people. Whatever the cause, the people did not vanish. Their descendants live on among many Native nations today. As you walk back down, notice the grass under your feet again. Remember that every step rests on the work of thousands of hands, and the soil still holds their story.