One morning last September, a warm red sun rose behind Monks Mound, inching above the level terrace where a tribal palace once stood, burning the mist off the flat green expanses of former plazas. To the west of the mound, in a circle more than 400 feet in diameter, several dozen cedar posts rise to the height of telephone poles. The woodhenge, as the structure is known, is a reconstruction of a series of circles found in the 1960s and ’70s when excavations to build a mammoth cloverleaf joining three interstate highways unearthed the remains of several hundred houses and dozens of post pits. (The findings persuaded the Federal Highway Administration to relocate the cloverleaf a few miles north.)
At the autumnal equinox, the rising sun aligns exactly with one post when viewed from the center of the circle, just as it does at the spring equinox and the solstices. William Iseminger, assistant site manager for the Cahokia Mounds State Historic Society, takes these alignments as evidence that the posts may have functioned as a kind of calendar, marking the turn of the seasons. Other woodhenges may have been part of lesser mounds, but, says Iseminger, they are nearly impossible to find because the post pits are so far apart, and wood rarely survives centuries underground.
Many archaeologists point to the size and ambition of structures like the woodhenge as evidence of Cahokia’s sophistication. The construction of Monks Mound, for example, used between 15 billion and 20 billion pounds of soil, which were lugged to the site in woven baskets that held 50 to 60 pounds of dirt each. Grading and draining the 40-acre plaza in front of it meant moving just as much earth. The stockade walls consumed 20,000 trees. Subsidiary mounds in the city “grid” seem to be placed according to a rational design. These accomplishments imply organized feats of labor and planning enacted by a central authority.
In many excavations, the number of artifacts and the amount of refuse indicate the population spiked sharply around A.D. 1100, jumping from hundreds to perhaps tens of thousands of people. Large homes and mounds appeared where villages of small houses had existed just a generation before. In the mid-1990s, excavations by Pauketat, Kelly, and others showed that the hills east of Cahokia were far more populous than anyone had suspected. A wooded rise among farmhouses in the city of O’Fallon marks the site of an ancient acropolis that probably served more than 500 people. At a site south of O’Fallon, Pauketat found remnants of 80 houses, three temples, clay pots, hoe blades, ax heads, and carved redstone statues. On a tree-lined street in Lebanon, a flagpole is planted in the center of a former platform mound marking another temple center.
Based on these findings, Pauketat estimates that as many as 50,000 people may have lived in Cahokia’s greater metropolitan area at the settlement’s peak. They seem to have appeared as if from nowhere. “Cahokia had to be created by large-scale migration from other places,” says Tom Emerson, director of the state transportation department’s archaeological program. “Nobody can breed that fast.”
Why did migrants come to Cahokia? Past theories suggested that the dual forces of nature and commerce drove the city’s rapid growth. The fertile bottomland was ripe for cultivation by farmers skilled in raising corn, squash, and sunflowers. The nearby confluence of the Illinois, Missouri, and Mississippi rivers could have put Cahokia at the nexus of trade networks that spanned much of the continent. But American Indians had been building modest mounds in the Mississippi River valley since 3500 B.C.; they’d been growing corn with much the same tools for hundreds of years, and the rivers and floodplains had been there for thousands. Economic and geographic felicities alone cannot account for the sudden concentration of people in the area at a particular moment.
Where in the world where the Cahokians?
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