Not forgotten, and not lost
Cahokia is not a lost city. It has been studied for well over a century, it is a UNESCO World Heritage Site, and Native nations of the region have their own connections to the area. “Forgotten” is better understood as meaning that it is far less known to the general public than comparable sites in Mexico or Peru. What is well established is that Cahokia, on the Mississippi floodplain in what is now southwestern Illinois, across the river from modern St Louis, was the largest settlement north of Mexico before European contact. The name Cahokia comes from a later Illinois-area people and is not what its builders called it, which is unknown.
Setting and rise
The site lies in the fertile “American Bottom”, where several rivers meet. People had lived in the region for thousands of years, and farmers there grew maize, squash and other crops, along with native seed plants. Around 1050 CE, the settlement grew very rapidly. Archaeologists often describe this as a sudden transformation, with large-scale building, planned plazas and an influx of people, and some suggest the change may have been linked to a religious or political movement. Causes are debated.
Dating relies on radiocarbon dating of wood and charcoal, backed by a ceramic chronology built on pottery seriation, since there is no written record. This gives the peak of the city as roughly 1050 to 1200 CE.
Monks Mound and the city plan
Monks Mound is the largest earthen mound in North America. It rises roughly 30 metres in several terraces, and its base covers about 14 acres. The name comes from Trappist monks who lived nearby in the early 1800s and grew vegetables on its terraces; it has nothing to do with the original builders. Built in stages over decades, it was constructed from basketloads of earth carried by people, without draft animals. A large building probably stood on its summit, perhaps the residence or ritual house of a leader.
South of Monks Mound lies the Grand Plaza, a leveled open space of many acres. Around it and across the site were once about 120 mounds, of which dozens survive. They had different forms and uses: flat-topped platform mounds for buildings, conical mounds for burials, and ridge-topped mounds as markers. A wooden palisade surrounded the central precinct and was rebuilt several times, which suggests concern about defence, though some scholars argue it also marked sacred space.
Woodhenge and Mound 72
Near the center, archaeologists found the traces of several successive circles of wooden posts, nicknamed Woodhenge. Some posts line up with sunrise at the solstices and equinoxes, and the circles are widely thought to have been used for marking the seasons, although the exact function is debated.
Mound 72, a small ridge-top mound south of Monks Mound, held some of the most dramatic burials. In one, an adult man was laid on a bed of tens of thousands of shell beads, accompanied by other people, and elsewhere in the mound groups of young women were buried together. Many archaeologists interpret these as sacrifices and as evidence of a hierarchy in which some people held great power. The details of how the mound was built and who was buried are still analysed today.
Population and society
Estimates of Cahokia’s population at its peak are usually somewhere between 10,000 and 20,000 for the main city, and higher if the surrounding farmland is included. These are estimates drawn from counts of house remains, and they carry real uncertainty. Even at the low end, the city was larger than most contemporary settlements in North America and comparable to some in Europe.
Mississippian society was organised around chiefs, or leaders whose authority combined religion and kinship. Evidence suggests a stratified society, with craft specialists, farmers and elites. Artifacts are decorated with recurring images such as the falcon-like “birdman”, which probably had religious meaning. Maize farming fed the population, and chunkey, a game with a rolling stone disc, was played in the plazas, as it was in much of the eastern woodlands.
Daily life
Most residents were farmers and craftspeople living in houses with walls of upright posts and thatched roofs, arranged around smaller courtyards and plazas. Food came from fields of maize and other crops, from fishing and from hunting deer and waterfowl. Specialists made shell beads, stone tools and pottery, and distinctive items such as flint figurines and carved stone pipes turn up across the site. Evidence from houses and food remains suggests that feasting played an important role, and large pits filled with debris from communal meals have been interpreted this way. Many details of family life, language and belief are unknown, since Cahokians left no writing.
Trade and connections
Goods found at Cahokia came from far away, including copper from the Great Lakes region, marine shell from the Gulf Coast and stone from various sources. Maize itself came ultimately from Mexico, but whether Cahokia had direct contact with Mesoamerican societies is not demonstrated; most researchers favor local development of its religion and politics.
Researchers continue to find new details of the layout, including with LiDAR survey, which can reveal earthworks hidden by vegetation and later development.
Decline
By around 1200 population began to fall, and by about 1350 the city was largely abandoned. No single cause is established. Proposed factors include flooding, the depletion of local timber and soil, political instability, conflict and changes in climate. As with other cases, such as the Classic Maya collapse or the Easter Island ecocide debate, a single explanation is rarely convincing, and several pressures may have combined. People did not vanish; they moved away and joined other communities.
Descendants and legacy
Mississippian peoples are ancestral to many Native nations of the Midwest and Southeast, and communities such as these maintain their own traditions about the past. Cahokia was occupied at about the same time as the Ancestral Puebloan migration that took people out of the Four Corners region, although the two had different societies and no simple link. Today the site is protected as a state historic site, and visitors can climb Monks Mound.