Genealogists often forget that U.S. history did not start in 1620. In fact, ancient peoples were here long before Europeans arrived on the shores of North America. Some of these people built advanced civilizations, dispelling the belief that all the previous inhabitants of North America were savages. For instance, a 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.
Cahokia flourished 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. The Cahokians made three different types of mounds -- pyramid-shaped (with flat tops upon which important officials' houses and ceremonial lodges were built), ridge-topped and conical. The latter two are believed to be used for burials of wealthy citizens and sacrificial victims. Archeologists have found that a large building -- 105 feet long, 48 feet wide and about 50 feet high -- was once positioned on top of the mound. It's believed to have been the home of Cahokia's rulers.
You can read more about Cahokia at http://www.wired.com/news/roadtrip/riverroad/0,2704,65170,00.html.