The missing Mississippians

What happened to Cahokia?

A traveler descending the Mississippi River around the year 1100 would have become aware, not far below the entrance of the Missouri River, of a large community of people beyond the left bank. Had the traveler landed and journeyed several miles east, he might have been surprised to discover a city of perhaps 20,000 people.

On the other hand, the traveler might not have been surprised at all. The city might have been the goal of his travels. Yet he still would have been struck, if he hadn't been there before, at the size of the city, which was the largest in the Americas north of the Valley of Mexico. Much as the residents of Tenochtitlan remodeled their landscape by filling in a lake and building pyramids, the residents of the Mississippi city improved on nature by piling dirt into great mounds that became the foundation for large buildings.

The name they gave their city was later lost to history. The name they gave to themselves was lost too. In fact the city itself was lost. At any rate the Cahokia people who inhabited the vicinity when Europeans arrived had no memory of a city and didn't know what the mounds signified. Yet the lost city has been called Cahokia by anthropologists who have been digging around in the ruins for decades.

It was the anthropologists who reconstructed the rise and fall of Cahokia. The residents of Cahokia doubtless chose the site for reasons similar to those that caused Europeans to build St. Louis. It stood at the junction of the two mightiest rivers of North America, facilitating access to two extensive river valleys. And the alluvial soil was deep and fertile, well suited to the cultivation of maize, which later Americans would call corn.

In the century to 1100, Cahokia grew into a large city. Commerce played a role in its growth. Food came from nearby, and manufactured articles from as far away as modern Pennsylvania have been found. Cahokia probably had religious significance. Some of the mounds seem to have been topped by temples, and numerous skeletons bear the marks of human sacrifice. Moreover, a wooden counterpart to England’s Stonehenge aligned posts in patterns of astronomical significance, which many traditional societies connected to deities.

There's no evidence Cahokia was a military power. On the contrary, remains of various walls indicate that it was the beset rather than the besetter. A city of this kind would have had stores of food and other items tempting to surrounding peoples.

Some time after 1200, Cahokia became terminally beset. The residents picked up and left. There is no sign of a great battle. No charred earth points to a conflagration. The Cahokians had no written language. Not even tally marks on pottery survive to indicate recordkeeping.

Perhaps the most puzzling thing is the absence of any memory of the city among the peoples later living in the area. In other parts of North America, cultural memories go back hundreds and thousands of years. Indians living along the lower Columbia River spun myths around eruptions of Cascade Mountain volcanoes that occurred centuries before their time. The Klamath Indians of southern Oregon have myths about the eruption that created Crater Lake almost 8,000 years ago.

No such echoes of Cahokia or its demise appear in the tales and legends of the peoples of the Mississippi Valley. It's almost as though the original Cahokians vanished along with the city. Either that or the demise occurred so gradually as not to seem a big deal. 

Anthropologists have proposed various explanations. Climate change and environmental degradation come readily to mind to modern researchers. There was a shift to drier and cooler weather around the time Cahokia was being abandoned. Yet recent research indicates the shift had comparatively little effect on local fauna. Cahokians must have cut down a lot of trees to build their temples and houses, which are known not to have been of stone, since no stone rubble remains. Some researchers proposed that deforestation caused flooding that drove the Cahokians away. But the silt one finds after floods is absent.

Perhaps squabbling among different groups rose to the level of civil war. Yet civil wars don't usually end with both sides abandoning the prize they were fighting over.

Did a plague depopulate the city? Probably not. Plagues of such virulence awaited the arrival of Europeans, who brought diseases to which the indigenous Americans had little resistance. Anyway, if a plague had killed half the population, the other half would have survived and presumably would have found the location still attractive. Paris lost a third of its population to the Black Death, but Paris wasn't abandoned by the survivors.

No, there was something that cost Cahokia its raison d'etre. Administering a large city requires a certain social and political cohesion. Researchers conjecture that Cahokia had a diverse population that for some reason lost its cohesion and dispersed. No single group had the wherewithal or incentive to maintain a city built for a much larger population. 

Or maybe Cahokia was less a city of residence than a place where people gathered for specific purposes. In the 1830s Indians, trappers and agents of fur trading companies met each summer for a rendezvous in the Rocky Mountains. Thousands of people—men, women and children—spent weeks together conducting business and doing the numerous other things people get together to do. During the time of the rendezvous, it formed the largest community west of the Missouri. Cahokia might have been an extended rendezvous. Analogously, millions of Muslims travel to Mecca each year as part of their religious practice, swelling that city’s population temporarily. Cahokia might have been a holy city to pilgrims.

If trade routes shifted, or religious practices changed, Cahokia could have become superfluous. When a supermarket closes or a parish loses members, people directly affected might lament the change, but no trauma is seared into the memory of the culture. Cahokia’s moment ended not with a bang but with a whimper. Maybe that’s why.

But we’re still only guessing.