Cahokia mounds , Illinois

At a time when settlements in the Americas rarely exceeded 400 or 500 inhabitants, the Native American center of Cahokia was as large as contemporary London, a size that no other city in the United States would attain until the nineteenth century. The well-organized aggregation of mounds and residential districts had a population estimated at 10,000 to 30,000—some sources claim 40,000. Cahokia’s distinctive earth mounds (there were 120 of them) took three forms: conical, “ridge top,” and, most commonly, platforms, often crowned with ceremonial buildings or the houses of the powerful. At the heart of the city stood the huge ceremonial embankment (now known as Monks Mound) that was in itself a stupendous feat of planning and engineering.

The indigenous American civilization known as Mississippian—no one knows what they called themselves—sprang up in the American Bottom, an extensive fertile floodplain near the confluence of the Mississippi, Missouri, Illinois, Kaskaskia, and Meramec Rivers. Between about a.d. 1000 and 1250, they lived near what is now central and East St. Louis and where the Illinois towns of Fairmont City, Dupo, Lebanon, and Mitchell now stand. This suburban concentration was eclipsed by their greatest achievement: Cahokia, dubbed “America’s lost metropolis.” Cahokia was named for the branch of the Illinois people who occupied the region in the seventeenth century, long after the builders had departed.

In terms of both agriculture and trade, Cahokia was perfectly located. The predictable annual flooding of farmland enabled planning and replenished the soil so that maize and other crops were sustainable for centuries. The river systems reaching out to much of North America facilitated trade, and there is evidence of commercial traffic over a network that extended from Minnesota in the north to Mississippi in the south; Cahokian traders reached west as far as Kansas and east to Tennessee. Raw materials such as copper, seashells, and mica were imported and processed in Cahokia to be exported as copper ornaments and shell beads—indications of a sophisticated manufacturing industry. It was once believed that this productive economic environment led to population growth, as Cahokian civilization slowly flowered.

Recently, archeologist Timothy Pauketat has questioned this conclusion, claiming that there is no evidence for it. Although not all his peers agree, he suggests that Cahokia experienced an urban implosion in little more than a decade early in the eleventh century a.d., growing from a village of only 1,000 into a city ten times that size. Based on studies of wider Native American beliefs, that event may have been due to the emergence of a charismatic chief whose arrival prompted villagers to abandon their settlements throughout eastern Missouri and southern Illinois and migrate to Cahokia.
It is now widely accepted that the Middle Mississippian area of which Cahokia forms a large part was under some kind of chiefdom government. Each chief—a Brother of the Sun—seems to have ruled a territory that depended upon a specific floodplain, and he managed food distribution between the central place and outlying settlements. Perhaps he had other roles, including matters of trade, administration of a civil service, and most probably religio-political duties. Little more is known.

However it came into being, the fact of Cahokia is staggering. Its earthen mounds extended over 6 square miles (15 square kilometers). At the heart of the city, defended by a wooden stockade, was the 200-acre (81-hectare) precinct of the ruling class, with the great ceremonial flat-topped mound at its center. The engineers and architects built to a master plan that was almost certainly based upon Mississippian cosmology—a sort of model of the universe. Cahokians viewed their universe as Father Sky and Mother Earth, and the layout of streets and structures mirrored that. The northern half of the city represented Sky, the southern half, Earth. They were defined by a long east-west street; another, running northeast, formed a cross symbolizing north, south, east, and west, its center point just in front of the central mound and at the end of a grand plaza. Archeologists have uncovered four circular solar calendars built of large, evenly spaced red cedar posts at the outer limits of the two streets. These “wood-henges,” so called because they had the same purpose as Stonehenge in England, were essential to the Cahokians’ agriculture-based economy, both in a practical and a ceremonial sense.

From about 1100 the central precinct, containing 17 earth mounds, was protected by a 2-mile-long (3.2-kilometer) stockade, constructed from some 15,000–20,000 1-foot-thick (30-centimeter) oak and hickory logs. The wall was about 12 feet (3.6 meters) high, with projecting bastions every 70 feet (21 meters) along its length. Outside it, thousands of single-family houses clustered, organized in small groups around ceremonial poles. Although it may have served as a social barrier between the Cahokian elite and the general population, it is clear from its form and the evidence of some hastily built parts that the palisade’s main purpose was defense. It was rebuilt three times before 1300.

The inner city of Cahokia was dominated by an enormous platform mound, identified as the largest prehistoric earthwork in the Americas. Surviving today, Monks Mound was named after a Trappist monastery in the vicinity. Its base, measuring 1,037 by 790 feet (291 by 236 meters), extends over 14 acres (5.25 hectares), and the structure rises through four sloping-sided rectangular terraces to a height of 100 feet (30.6 meters). It contains 820,000 cubic yards (692,000 cubic meters) of earth, all of which was hand-excavated from large “borrow” pits and carried in woven baskets to the site. Monks Mound was built in several stages over about 200 years, with carefully designed strata of sand and clay, and drains to deal with water saturation. Long ago, it was crowned with a 50-foot-high (15-meter) thatched-roof building of timber-pole construction, 105 by 48 feet (31 by 14 meters). Some scholars identify it as a temple. It was certainly the chief’s residence, in which the political and religious observances were conducted that ensured the nation’s continuing prosperity. In effect, the mound was a means of lifting Mother Earth to Father Sky, bringing male and female together. That these ancient builders could set out their city with its streets aligned to the cardinal compass points and construct such a durable monument over generations, without having a written language or the wheel, makes their accomplishment the more marvelous.

Around 1200, for reasons that may only be guessed, Cahokia began to decline. Perhaps growth had placed too much burden upon the agricultural hinterland or overloaded the urban infrastructure; perhaps deforestation had changed the local ecology. Or perhaps there was civil war over dwindling resources. Other scholars attribute the demise of the city to a mud slide on the great mound, which may have been construed as an omen. No one really knows. And no one knows where the Cahokians went. By 1400 their remarkable metropolis was abandoned. Arriving much later in the area, the first Europeans mistook the mounds, overgrown by then, for natural hillocks. Monks Mound was not discovered until the beginning of the nineteenth century.

Modern farming, expanding towns, highways, and pollution continue to threaten those smaller communities around Cahokia that have not already been destroyed. The 2,200-acre (890-hectare) Cahokia Mounds State Historic Site is administered by the Illinois Historic Preservation Agency. It was added to UNESCO’s World Heritage List in 1982. Archeological investigation continues. Following major slumps on the east and west sides of Monks Mound in the mid-1980s, attempts were made to reduce internal waterlogging. In January 1998 construction workers, drilling horizontally into the west side, struck a deep layer of limestone or sandstone cobbles 40 feet (12 meters) beneath the surface. Further tests were hampered by groundwater, but the find has excited scientists because stone does not naturally occur in the region. There is much more to be revealed at Cahokia.