While there were great pre-Columbian cities in Mesoamerica (like the Aztecs and the Maya) and in South America (like the Inca), there weren't the same sort of great cities in what is today the United States. One time when North America did have a large thriving city was 1,000 to 600 years ago called Cahokia.

The history of Cahokia is a mysterious and intriguing one, and everyone should visit. There are many theories for why Cahokia was abandoned, but now research has shown that one of the leading theories is wrong and so its story remains more of a mystery than ever.

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What to Know About the Cahokia Mounds

Today the Cahokia Mounds are part of the Cahokia Mounds State Historic Site just out of St. Louis but across the river in Illinois. The site contains around 80 mounds and covers around 3.5 square miles. The ancient city was much larger than that though, and it covered around 6 square miles at its peak.

  • Date: Cahokia Existed Circa 1050 to 1350 AD
  • Apex: Around 1100 AD
  • Deserted: Around 1400 AD
  • Population: Perhaps 15,000

Cahokia is built on a floodplain called the American Bottom. Its population was perhaps 15,000 in the city itself with around twice that in the surrounding areas. Prior to European contact, it was the most densely populated place in North America (excluding Mesoamerica).

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It Wasn't Because of Environmental Degradation

But at least if archeologists don't know what did trigger its decline, they can rule out one thing that didn't. One of the leading suggestions for why Cahokia declined was because of flooding brought on by the over-harvesting of timber in the area. The theory was that this made the region increasingly uninhabitable due to deforestation that led to flooding that led to diminished harvests and the flooding of residential areas.

  • Ecocide: The Idea That Society Fail Due To the Degradation of The Environment Is Called "Ecocide"
  • Leading Theory: Ecocide Had Been The Dominate Explanation For Cahokia For The Last Half Century

But recently National Geographic reported on a study published in the journal Geoarchaeology by Caitlin Rankin of the University of Illinois. This study concludes that Cahokia was not damaged by environmental degradation. They failed to find any evidence that there was recurrent flooding of the sort predicted by the wood-overuse hypothesis.

The research showed that the soil remained stable over that time and there was no evidence of flood sediments.

While ecocide has been responsible for the death of many Old World civilizations, the people of North America didn't graze animals or intensively plow.

Who The Cahokians Were

The Cahokians cultivated corn and various other crops and were part of what is called the Mississippian culture. Mostly they lived in a Diaspora of agricultural communities throughout the American Southwest. But just why they gathered and formed into a highly concentrated urban now known as Cahokia remains a mystery.

Mississippian Culture:

  • Existed: Between 800 and 1500 AD
  • Where: Across The American Southeast

Why they formed the greatest city in North America is a question remaining to be answered satisfactorily.

Perhaps it was for some sort of mixture of political, religious, or economic reasons.

Related: Myth and Hypothesis: Could The Lost City Of Atlantis Be Found?

Why Was Cahokia Abandoned?

Cahokia is one of those sites that has mystified archeologists. Its earthen mounds include one that rose 10 stories into the air. Until 1867, this mound remained the tallest manmade structure in the United States.

What We Don't Know:

  • Why Cahokia Developed
  • Why Cahokia Became Powerful
  • Why People Abandoned Cahokia

While we don't know the answers to these questions, there are plenty of theories - but the issue is scant evidence. In the future, there are likely to be more theories as to why Cahokia declined and collapsed. And these theories are likely to become more complex.

Their decline didn't happen overnight, and it was a slow demise. This could have been driven by some sort of storm of events like warfare, drought, disease, and political factionalization. We just don't know - but it is not known that what was the most popular theory is wrong.

The stockade the Cahokians built that encircled central Cahokia would suggest warfare becoming a problem. There is also some evidence of a major drought in the region. But these are all currently under investigation and hopefully, there will be more answers in the future.

It is often tempting to think of time as progress. Over time with evolution, organizations get more complex and smart, and over time civilizations develop more technology and grow in complexity. But this is not what happens at all. The complex society that once rose in the Mississippi disappeared and the reasons for that continue to be debated.