Cahokia

They were mound builders.

The Mississippian town of Cahokia was a thriving urban market center. Archaeologists excavating Cahokia found a planned city that included pyramid mounds of packed earth arranged around huge open plazas, temples and astronomical observatories, and thousands of thatched-roof houses. The remains of Cahokia's mounds can still be seen after five hundred years of erosion.

Founded around AD 700. Cahokia was sent into decline by the fourteenth century from increasing social unrest, floods caused by upriver deforestation, and an earthquake in the thirteenth century. Most likely, the growing population of the town had exhausted the resources needed to support it in a period of climatic change; archaeological evidence suggests there also may have been increasing pressure from enemies.

Cahokia was near the confluence of the Missouri, Mississippi, and Illinois rivers and occupied for about seven hundred years.

Cahokia at its height was the contemporary of Chaco and had a population between 10,000 to 30,000 or about the population of medieval London. Cahokia was the largest settlement to have existed north of the Rio Grande before the end of the eighteenth century. Trade routes linked Cahokia to distant regions of the continent. The Cahokia mounds offer impressive testimony to a civilization that developed before Europe entered its Middle Ages, flourished longer than the United States existed as a nation, and declined before Europeans set foot in America.