Long ago, tens of thousands of residents populated an area east of modern day St. Louis we call today as Cahokia. Starting in about 700 A.D. and lasting about 600 years, this metropolis rivaled in size other large cities such as London. Around 1000 A.D., the area exploded in growth from about 1000 to 15,000 (some say even 40,000) people in just 100 years. With certainty it was the largest and most advanced city north of Mexico before Columbus arrived.
© Cahokia Mounds Museum SocietyArtist's rendition of Cahokia Mounds
One hundred and twenty earthen mounds were built solely with human hands by moving dirt with stone hoes and woven baskets. Five large and extremely accurate cedar pole solar calendars similar to Stonehenge were constructed in a central plaza. Sophisticated wooden buildings were built for ritual and residential purposes. Trade was conducted with other societies thousands of miles away. A defensive wall with watch towers circled the city. They had a prominent, central system of government made up of chiefs, religious leaders and an elite class. Lesser class citizens grew crops for the upper class and other urban residents who were mainly tradesmen and artisans.

And then they were gone.

All that remains today are the earthen mounds. When the French missionaries explored the area, they asked the local Illini tribe about the structures. The natives had come into the area just before the Europeans and did not know of the mounds' history. So the monks conveniently named the largest, Monk's Mound after themselves. (For many years the mounds were thought to be naturally formed. It wasn't until 1921 that archaeological evidence showed that they were actually man-made.)
© Cahokia Mounds Museum SocietyArtist's rendition of Cahokia Mounds in 1150 AD
We have no idea what ethnicity they were or what language they spoke. We don't even know what the group called themselves. 'Cahokia' actually comes from the name of the subtribe of the Illinois people that lived nearby.

Most importantly, we don't know why they left. Some say that Cahokia's end came as the result of its overuse of nearby timber or hunting resources. Maybe it was disease. Perhaps it was the pollution from all the cooking fires or the lack of crop diversity. Some even say that aliens took them away.

All we can do is speculate, as I am doing. But I wonder if it had to do with the local weather.

Statistically this area has always been a hotbed of tornadic activity. In May 1896, the nation's third costliest and deadliest tornado hit St. Louis and crossed the river into Madison county killing 255 (some say 400+) people. Add to that disastrous storms in 1871, 1890, 1904, 1927, and 1959 when a total of 117 were killed, this makes the St. Louis region one of the hardest hit metropolitan areas in the U.S. I count that no less than 91 twisters have touched down in the metro area since the 1870's, including last year's Good Friday EF4 which ran across north St. Louis County and Lambert Airport and into Illinois. Being in such an active area, the wood post structures of Cahokia would have been no match for the killer winds.
© Cahokia Mounds Musem SocietyCahokia today
The American Bottoms region has long been known for its fertile ground. Located near the confluence of the Mississippi and Missouri Rivers and the nearby Illinois, the area endured the blessings and the curses that came as a result of the rivers overflowing their banks. That is until the series of locks and dams were built along the Mississippi in the 1930's. But before that time there would be no stopping of the annual spring floods of muddy water. The Cahokia community was centrally located inside the floodplain, the widest such north of New Orleans. In 1844 floodwaters moved all the way to the nearby bluffs more than a mile from the river, surrounding the mounds themselves. This occurred again in 1849. In 1903 a flood washed away two to three FEET of ground just northeast of Monk's Mound. Two or three consecutive years of these damaging floods would have decimated Cahokia's crop for the year and prevented having enough seed for the next.

What warning would the ancient culture of Cahokia have about an approaching storm? Even the best network of ancient storm spotters beating drums and blowing conch shells couldn't get the message through in time. What protection would they have had cowering in ground level wooden housing from the 200 tornadic mph winds? Recent images of Harrisburg and southern Indiana make this image so vivid. How could they survive the onset of floods, the removal of fertile topsoil and the muck and mire left behind?

Just wondering....