Cahokia was one big piece in the mosaic of chiefdoms that covered the lower half of the Mississippi and the Southeast at the end of the first millennium A.D. Known collectively as “Mississippian” cultures, these societies arose several centuries after the decline of the Hopewell culture, and probably were its distant descendants. At any one time a few larger polities dominated the dozens or scores of small chiefdoms. Cahokia, biggest of all, was preeminent from about 950 to about 1250 A.D. It was an anomaly: the greatest city north of the Río Grande, it was also the only city north of the Río Grande. Five times or more bigger than any other Mississippian chiefdom, Cahokia’s population of at least fifteen thousand made it comparable in size to London, but on a landmass without Paris, Córdoba, or Rome.

I call Cahokia a city so as to have a stick to beat it with, but it was not a city in any modern sense. A city provides goods and services for its surrounding area, exchanging food from the countryside for the products of its sophisticated craftspeople. By definition, its inhabitants are urban—they aren’t farmers. Cahokia, however, was a huge collection of farmers packed cheek by jowl. It had few specialized craftworkers and no middle-class merchants. On reflection, Cahokia’s dissimilarity to other cities is not surprising; having never seen a city, its citizens had to invent every aspect of urban life for themselves.

Despite the nineteenth-century fascination with the mounds, archaeologists did not begin to examine Cahokia thoroughly until the 1960s. Since then studies have gushed from the presses. By and large, they have only confirmed Cahokia’s status as a statistical outlier. Cahokia sat on the eastern side of the American Bottom. Most of the area has clayey soil that is hard to till and prone to floods. Cahokia was located next to the largest stretch of good farmland in the entire American Bottom. At its far edge, a forest of oak and hickory topped a line of bluffs. The area was little settled until as late as 600 A.D., when people trickled in and formed small villages, groups of a few hundred who planted gardens and boated up and down the Mississippi to other villages. As the millennium approached, the American Bottom had a resident population of several thousand. Then, without much apparent warning, there was, according to the archaeologist Timothy R. Pauketat of the University of Illinois at Urbana-Champaign, what has been called a “Big Bang”—a few decades of tumultuous change.

Cahokia’s mounds emerged from the Big Bang, along with the East St. Louis mound complex a mile away (the second biggest, after Cahokia, though now mostly destroyed) and the St. Louis mounds just across the Mississippi (the fourth biggest). Monks Mound was the first and most grandiose of the construction projects. Its core is a slab of clay about 900 feet long, 650 feet wide, and more than 20 feet tall. From an engineering standpoint, clay should never be selected as the bearing material for a big earthen monument. Clay readily absorbs water, expanding as it does. The American Bottom clay, known as smectite clay, is especially prone to swelling: its volume can increase by a factor of eight. Drying, it shrinks back to its original dimensions. Over time the heaving will destroy whatever is built on top of it. The Cahokians’ solution to this problem was discovered mainly by Woods, the University of Kansas archaeologist and geographer, who has spent two decades excavating Monks Mound.

To minimize instability, he told me, the Cahokians kept the slab at a constant moisture level: wet but not too wet. Moistening the clay was easy—capillary action will draw up water from the floodplain, which has a high water table. The trick is to stop evaporation from drying out the top. In an impressive display of engineering savvy, the Cahokians encapsulated the slab, sealing it off from the air by wrapping it in thin, alternating layers of sand and clay. The sand acts as a shield for the slab. Water rises through the clay to meet it, but cannot proceed further because the sand is too loose for further capillary action. Nor can the water evaporate; the clay layers atop the sand press down and prevent air from coming in. In addition, the sand lets rainfall drain away from the mound, preventing it from swelling too much. The final result covered almost fifteen acres and was the largest earthen structure in the Western Hemisphere; though built out of unsuitable material in a floodplain, it has stood for a thousand years.


Reconstructions of Cahokia, the greatest city north of the Río Grande, ca. 1250 A.D.

Because the slab had to stay moist, it must have been built and covered quickly, a task requiring a big workforce. Evidence suggests that people moved from miles around to the American Bottom to be part of the project. If the ideas of Pauketat, the University of Illinois archaeologist, are correct, the immigrants probably came to regret their decision to move. To his way of thinking, the Big Bang occurred after a single ambitious person seized power, perhaps in a coup. Although his reign may have begun idealistically, Cahokia quickly became an autocracy; in an Ozymandiac extension of his ego, the supreme leader set in motion the construction projects. Loyalists forced immigrants to join the labor squads, maintaining control with the occasional massacre. Burials show the growing power of the elite: in a small mound half a mile south of Monks Mound, archaeologists in the late 1960s uncovered six high-status people interred with shell beads, copper ornaments, mica artworks—and the sacrificed bodies of more than a hundred retainers. Among them were fifty young women who had been buried alive.

Woods disagrees with what he calls the “proto-Stalinist work camp” scenario. Nobody was forced to erect Monks Mound, he says. Despite the intermittent displays of coercion, he says, Cahokians put it up “because they wanted to.” They “were proud to be part of these symbols of community identity.” Monks Mound and its fellows were, in part, a shout-out to the world—Look at us! We’re doing something different! It was also the construction of a landscape of sacred power, built in an atmosphere of ecstatic religious celebration. The American Bottom, in this scenario, was the site of one of the world’s most spectacular tent revivals. Equally important, Woods says, the mound city was in large part an outgrowth of the community’s previous adoption of maize.

Before Cahokia’s rise, people were slowly hunting the local deer and bison populations to extinction. The crops in the Eastern Agricultural Complex could not readily make up the difference. Among other problems, most had small seeds—imagine trying to feed a family on sesame seeds, and you have some idea of what it would have been like to subsist on maygrass. Maize had been available since the first century B.C. (It would have arrived sooner, but Indians had to breed landraces that could tolerate the cooler weather, shorter growing seasons, and longer summer days of the north.) The Hopewell, however, almost ignored it. Somewhere around 800 A.D. their hungry successors took another look at the crop and liked what they saw. The American Bottom, with its plenitude of easily cleared, maize-suitable land, was one of the best places to grow it for a considerable distance. The newcomers needed to store their harvests for the winter, a task most efficiently accomplished with a communal granary. The granary needed to be supervised—an invitation to develop centralized power. Growth happened fast and may well have been hurried along by a charismatic leader, Woods said, but something like Cahokia probably would have happened anyway.



Maize also played a role in the city’s disintegration. Cahokia represented the first time Indians north of the Río Grande had tried to feed and shelter fifteen thousand people in one place, and they made beginner’s mistakes. To obtain fuel and construction material and to grow food, they cleared trees and vegetation from the bluffs to the east and planted every inch of arable land. Because the city’s numbers kept increasing, the forest could not return. Instead people kept moving further out to get timber, which then had to be carried considerable distances. Having no beasts of burden, the Cahokians themselves had to do all the carrying. Meanwhile, Woods told me, the city began outstripping its water supply, a “somewhat wimpy” tributary called Canteen Creek. To solve both of these problems at once, the Cahokians apparently changed its course, which had consequences that they cannot have anticipated.

Nowadays Cahokia Creek, which flows from the north, and Canteen Creek, which flows from the east, join together at a point about a quarter mile northeast of Monks Mound. On its way to the Mississippi, the combined river then wanders, quite conveniently, within two hundred yards of the central plaza. Originally, though, the smaller Canteen Creek alone occupied that channel. Cahokia Creek drained into a lake to the northwest, then went straight to the Mississippi, bypassing Cahokia altogether. Sometime between 1100 and 1200 A.D., according to Woods’s as-yet unpublished research, Cahokia Creek split in two. One fork continued as before, but the second, larger fork dumped into Canteen Creek. The combined river provided much more water to the city—it was about seventy feet wide. And it also let woodcutters upstream send logs almost to Monks Mound. A natural inference, to Woods’s way of thinking, is that the city, in a major public works project, “intentionally diverted” Cahokia Creek.

In summer, heavy rains lash the Mississippi Valley. With the tree cover stripped from the uplands, rainfall would have sluiced faster and heavier into the creeks, increasing the chance of floods and mudslides. Because the now-combined Cahokia and Canteen Creeks carried much more water than had Canteen Creek alone, washouts would have spread more widely across the American Bottom than would have been the case if the rivers had been left alone. Beginning in about 1200 A.D., according to Woods, Cahokia’s maize fields repeatedly flooded, destroying the harvests.

The city’s problems were not unique. Cahokia’s rise coincided with the spread of maize throughout the eastern half of the United States. The Indians who adopted it were setting aside millennia of tradition in favor of a new technology. In the past, they had shaped the landscape mainly with fire; the ax came out only for garden plots of marshelder and little barley. As maize swept in, Indians burned and cleared thousands of acres of land, mainly in river valleys. As in Cahokia, floods and mudslides rewarded them. (How do archaeologists know this? They know it from sudden increases in river sedimentation coupled with the near disappearance of pollen from bottomland trees in those sediments.) Between about 1100 and 1300 A.D., cataclysms afflicted Indian settlements from the Hudson Valley to Florida.

Apparently the majority learned from mistakes; after this time, archaeologists don’t see this kind of widespread erosion, though they do see lots and lots of maize. A traveler in 1669 reported that six square miles of maize typically encircled Haudenosaunee villages. This estimate was very roughly corroborated two decades later by the Marquis de Denonville, governor of New France, who destroyed the annual harvest of four adjacent Haudenosaunee villages to deter future attacks. Denonville reported that he had burned 1.2 million bushels of maize—42,000 tons. Today, as I mentioned in Chapter 6, Oaxacan farmers typically plant roughly 1.25–2.5 acres to harvest a ton of landrace maize. If that relation held true in upstate New York—a big, but not ridiculous assumption—arithmetic suggests that the four villages, closely packed together, were surrounded by between eight and sixteen square miles of maize fields.

Between these fields was the forest, which Indians were subjecting to parallel changes. Sometime in the first millennium A.D., the Indians who had burned undergrowth to facilitate grazing began systematically replanting large belts of woodland, transforming them into orchards for fruit and mast (the general name for hickory nuts, beechnuts, acorns, butternuts, hazelnuts, pecans, walnuts, and chestnuts). Chestnut was especially popular—not the imported European chestnut roasted on Manhattan street corners in the fall, but the smaller, soft-shelled, deeply sweet native American chestnut, now almost extinguished by chestnut blight. In colonial times, as many as one out of every four trees in between southeastern Canada and Georgia was a chestnut—partly the result, it would seem, of Indian burning and planting.

Hickory was another favorite. Rambling through the Southeast in the 1770s, the naturalist William Bartram observed Creek families storing a hundred bushels of hickory nuts at a time. “They pound them to pieces, and then cast them into boiling water, which, after passing through fine strainers, preserves the most oily part of the liquid” to make a thick milk, “as sweet and rich as fresh cream, an ingredient in most of their cookery, especially hominy and corncakes.” Years ago a friend and I were served hickory milk in rural Georgia by an eccentric backwoods artist named St. EOM who claimed Creek descent. Despite the unsanitary presentation, the milk was ambrosial—fragrantly nutty, delightfully heavy on the tongue, unlike anything I had encountered before.

Within a few centuries, the Indians of the eastern forest reconfigured much of their landscape from a patchwork game park to a mix of farmland and orchards. Enough forest was left to allow for hunting, but agriculture was an increasing presence. The result was a new “balance of nature.”

From today’s perspective, the success of the transition is striking. It was so sweeping and ubiquitous that early European visitors marveled at the number of nut and fruit trees and the big clearings with only a dim apprehension that the two might be due to the same human source. One reason that Bartram failed to understand the artificiality of what he saw was that the surgery was almost without scars; the new landscape functioned smoothly, with few of the overreaches that plagued English land management. Few of the overreaches, but not none: Cahokia was a glaring exception.

A friend and I visited Cahokia in 2002. Woods, who lived nearby, kindly agreed to show us around. The site is now a state park with a small museum. From Monks Mound we walked halfway across the southern plaza and then stopped to look back. From the plaza, Woods pointed out, the priests at the summit could not be seen. “There was smoke and noise and sacred activity constantly going on up there, but the peasants didn’t know what they were doing.” Nonetheless, average Cahokians understood the intent: to assure the city’s continued support by celestial forces. “And thatjustification fell apart with the floods,” Woods said.

There is little indication that the Cahokia floods killed anyone, or even led to widespread hunger. Nonetheless, the string of woes provoked a crisis of legitimacy. Unable to muster the commanding vitality of their predecessors, the priestly leadership responded ineffectively, even counterproductively. Even as the flooding increased, it directed the construction of a massive, two-mile-long palisade around the central monuments, complete with bastions, shielded entryways, and (maybe) a catwalk up top. The wall was built in such a brain-frenzied hurry that it cut right through some commoners’ houses.

Cahokia being the biggest city around, it seems unlikely that the palisade was needed to deter enemy attack (in the event, none materialized). Instead it was probably created to separate elite from hoi polloi, with the goal of emphasizing the priestly rulers’ separate, superior, socially critical connection to the divine. At the same time the palisade was also intended to welcome the citizenry—anyone could freely pass through its dozen or so wide gates. Constructed at enormous cost, this porous architectural folly consumed twenty thousand trees.

More consequential, the elite revamped Monks Mound. By extending a low platform from one side, they created a stage for priests to perform ceremonies in full view of the public. According to Woods’s acoustic simulations, every word should have been audible below, lifting the veil of secrecy. It was the Cahokian equivalent of the Reformation, except that the Church imposed it on itself. At the same time, the nobles hedged their bets. Cahokia’s rulers tried to bolster their position by building even bigger houses and flaunting even more luxury goods like fancy pottery and jewelry made from exotic semiprecious stones.

It did no good. A catastrophic earthquake razed Cahokia in the beginning of the thirteenth century, knocking down the entire western side of Monks Mound. In 1811 and 1812 the largest earthquakes in U.S. history abruptly lifted or lowered much of the central Mississippi Valley by as much as twelve feet. The Cahokia earthquake, caused by the same fault, was of similar magnitude. It must have splintered many of the city’s wood-and-plaster buildings; fallen torches and scattered cooking fires would have ignited the debris, burning down most surviving structures. Water from the rivers, shaken by the quake, would have sloshed onto the land in a mini-tsunami.

Already reeling from the floods, Cahokia never recovered from the earthquake. Its rulers rebuilt Monks Mound, but the poorly engineered patch promptly sagged. Meanwhile the social unrest turned violent; many houses went up in flames. “There was a civil war,” Woods said. “Fighting in the streets. The whole polity turned in on itself and tore itself apart.”

For all their energy, Cahokia’s rulers made a terrible mistake: they did not attempt to fix the problem directly. True, the task would not have been easy. Trees cannot be replaced with a snap of the fingers. Nor could Cahokia Creek readily be reinstalled in its original location. “Once the water starts flowing in the new channel,” Woods said, “it is almost impossible to put it back in the old as the new channel rapidly downcuts and establishes itself.”

Given Cahokia’s engineering expertise, though, solutions were within reach: terracing hillsides, diking rivers, even moving Cahokia. Like all too many dictators, Cahokia’s rulers focused on maintaining their hold over the people, paying little attention to external reality. By 1350 A.D. the city was almost empty. Never again would such a large Indian community exist north of Mexico.

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