Centuries before Christopher Columbus set foot in the Americas, a colossal city along the floodplains of the Mississippi River was buzzing along with its thousands upon thousands of residents. Little of the grand metropolis remains today except for a scattering of grassy hills, known as the Cahokia Mounds.
Just a short drive from St Louis in Missouri, the Cahokia Mounds are the remains of the largest pre-Columbian settlement north of Mexico (at least that modern-day archaeologists know about). It served as a vibrant economic hub of the Mississippian culture, which dominated the region from 800 to 1350 CE.
The settlement reached its peak between 1050 and 1150 CE when it covered around 1,600 hectares (4,000 acres) of land. Estimates vary, but it’s believed it held a population of somewhere between 10,000 to 50,000 people.
Around 51 of the settlement's original 120 earthen mounds still stand today. The most prominent is the so-called Monks Mound, the largest prehistoric earthen structure in the whole of the Americas.
This large platform mound rises in four terraces to a height of 30 meters (98 feet). It was constructed using piles of soil and clay packed on top of each other until they formed a steep hill. In its prime, it likely stood more upright, but the slopes have slumped over the centuries. Some researchers have argued that Monks Mound might have taken as long as 250 years to fully build, but more recent evidence suggests its construction could have been possible within just 20 years.
While not as mighty as the Great Pyramid of Giza in their size or grandeur, it’s worth remembering that these mounds were constructed without wheels, metal tools, or beasts of burden like horses or oxen.
Cahokia also featured an astronomical observatory, known as “Woodhenge”, made up of wooden posts evenly spaced around a circle like numbers on a clock. Archaeologists believe this structure was aligned to the position of the Sun in the sky during the summer solstice and the winter solstice, as well as the spring and fall equinox.
Some believe this city was already deserted and left to ruin by the time European colonizers arrived on American soil in the 15th century CE. The reason for its untimely demise is not agreed upon but there are a range of theories, ranging from drought and persistent flooding to war and social collapse.
However, a study in 2020 argued the story of Cahokia’s fall isn’t as clear-cut. They found evidence that the Native Americans repopulated the region in the 16th century CE and kept a steady presence there through the 18th century.
"One would think the Cahokia region was a ghost town at the time of European contact, based on the archeological record, but we were able to piece together a Native American presence in the area that endured for centuries," AJ White, lead author of the 2020 study and UC Berkeley doctoral student in anthropology, said in a statement.
“There’s very little archaeological evidence for an Indigenous population past Cahokia, but we were able to fill in the gaps through historical, climatic, and ecological data, and the linchpin was the fecal stanol evidence,” White added.
"The story of Cahokia was a lot more complex than, 'Goodbye, Native Americans. Hello, Europeans'."