From Indian Mounds Mystify Excavators:
A thousand years ago along the banks of the Mississippi River, in what is currently southeast Illinois, there was a city that now mystifies both archeologists and anthropologists.At its zenith, around A.D. 1050, the city that is now called Cahokia was among the largest metropolitan centers in the world. About 15,000 people lived in the city, with another 15,000 to 20,000 residing in its surrounding ‘suburbs’ and outlying farmlands. It was the region’s capital city, a place of art, grand religious rituals and science.
But by 1300, the city had become a ghost town, its carefully built structures abandoned and its population dispersed.
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Cahokia is not the historical name of this city; the current name comes from the native people who were living in the area when French explorers arrived in the early 1600s. The city’s authentic name — the name given to it by its creators — is lost to time, as its residents did not appear to have a written language.But what really puzzles archeologists and anthropologists is that there are no legends, no records, no mention whatsoever of the once-grand city in the lore of any of the tribes — Osage, Omaha, Ponca and Quapaw — that are believed to be the direct descendents of the city’s builders.
This odd silence on the matter of Cahokia has led some experts to theorize that something particularly nasty happened there.