Travel with Billy Carson — Cahokia Mounds is the remains of Cahokia, the largest city built by the Mississippian culture and the largest pre-Columbian settlement north of Mexico. It sits on the Mississippi River floodplain in south-western Illinois, across the river from modern St. Louis, and at its peak, roughly 1050 to 1150 CE, it may have held 10,000 to 20,000 people. Its best-known features are Monks Mound, the timber circles called Woodhenge, and the burials of Mound 72.
Cahokia matters because it overturns a common assumption about North America before Columbus. Native American builders laid out a planned city with plazas, more than a hundred earthen mounds, a solar calendar of wooden posts and a hierarchy visible in its graves. UNESCO inscribed the protected core as a World Heritage Site in 1982, and archaeologists still debate why the city emptied.
What and where was Cahokia?
Cahokia was the political and ceremonial centre of the Mississippian world, a set of farming societies that spread across the Mississippi valley and the American South from about 800 to 1400 CE. The city grew on a broad stretch of floodplain called the American Bottom, where rich soils supported maize farming alongside fishing, hunting and the gathering of wild plants.
At its height the settlement covered nearly 1,600 hectares and included about 120 mounds, according to UNESCO. Its main florescence is usually placed between about 1050 and 1350 CE. Population figures are estimates built from excavated houses and neighbourhoods, which is why ranges are given.
Today the Cahokia Mounds State Historic Site protects 541 hectares, including 51 platform, ridgetop and conical mounds. The rest of the ancient city lies under farmland, highways and the suburbs of the Metro East. UNESCO listed it under criteria (iii) and (iv) and approved a minor boundary change in 2016.
Who built Cahokia?
Cahokia was built by Native Americans of the Mississippian culture, and the archaeological record of its houses, pottery, tools, burials and food remains leaves no doubt on that point.
The question is worth answering plainly because of the nineteenth-century "Mound Builder" myth. As settlers moved west, many writers refused to credit Native Americans with the great earthworks of the Ohio and Mississippi valleys and invented a vanished race of builders instead, variously imagined as Welsh, Danes, Israelites or refugees from Atlantis. The idea suited people who wanted to justify taking Native land. A survey by the Smithsonian Institution's Bureau of Ethnology, led by Cyrus Thomas and published in 1894, concluded that the mounds were the work of the ancestors of Native Americans, and the myth has been regarded as debunked ever since.
Mound-building in the region was also far older than Cahokia. The earthworks of Poverty Point in Louisiana, now a World Heritage Site in their own right, were built and used by hunter-gatherers between about 1700 and 1100 BCE, more than two thousand years before Monks Mound rose.
Monks Mound: how big is it and what stood on top?
Monks Mound is the largest prehistoric earthen structure in the Americas. It stands about 30 metres high in four terraces, and its base covers between 5 and 6 hectares, comparable in footprint to the Great Pyramid of Giza, although it is earth rather than cut stone and much lower.
It was built by hand. Workers carried soil in baskets from borrow pits nearby and piled it in many stages over a long period; UNESCO counts fourteen construction stages. Excavations on the summit found evidence of a very large building, generally interpreted as the residence or temple of the city's leading figure or a place of major ceremonies.
The mound faces the Grand Plaza, a levelled open space ringed by other platform mounds. By around 1200 a wooden palisade enclosed this central precinct, which archaeologists read as a sign of rising tension, from outside threats or from divisions within the city.
The name has nothing to do with the builders. Trappist monks lived on a nearby, smaller mound between 1809 and 1813, and the writer Henry Brackenridge, who visited during those years and published the first detailed description, gave the great mound its modern name.
What was Cahokia's Woodhenge?
Woodhenge is the name given to a series of large circles of wooden posts that stood west of Monks Mound, and most archaeologists interpret them as solar calendars. Warren Wittry identified the first post pits in the early 1960s during salvage archaeology ahead of a planned highway interchange, and Robert Hall carried out further excavation in 1963, using the predicted arcs to locate more posts.
Five circles are now recognised, Woodhenges I to V. Each is larger than the last and has more posts: 24, 36, 48, 60 and possibly 72, though only part of the fifth circle has been found. They are dated roughly 900 to 1100 CE. From the centre of Woodhenge III, built around 1000 CE, the equinox sun appears to rise out of the front of Monks Mound, and the winter-solstice sunrise post lines up with Fox Mound to the south-east. Those alignments are the reason the calendar interpretation is widely accepted. Suggestions that the circles also tracked the moon or particular stars remain speculative.
A reconstruction of Woodhenge III was raised in 1985. The nickname invites comparison with Stonehenge, and the two monuments do share a basic idea, marking the sun's turning points with posts or stones set around a centre. They were built thousands of years and an ocean apart, though, and there is no evidence of any connection between them. Similar solar alignments appear in many independent cultures, including the Maya at Chichén Itzá.
What was found in Mound 72?
Mound 72 is a small ridgetop mound south of Monks Mound that holds the remains of about 270 people, buried in several episodes, and it is the main evidence that Cahokia practised large-scale human sacrifice. The archaeologist Melvin Fowler began excavating it in 1967 after predicting the location of a large post connected to the woodhenge system.
The most famous find is the "beaded burial." Two central bodies lay with a cape or platform of thousands of marine-shell beads, with counts of about 10,000 to 20,000 given, arranged in the shape of a bird. For decades the main body was read as a male chief or "warrior king," a reading that fitted the bird imagery, including the figure often called the Birdman, found widely in Mississippian art.
In 2016 Thomas Emerson, Kristin Hedman and colleagues published a reanalysis in American Antiquity, "Paradigms Lost: Reconfiguring Cahokia's Mound 72 Beaded Burial." Re-examining the skeletons, they found that the two central individuals were a man and a woman, that the beaded burial involved twelve people rather than the six previously reported, and that further male-female pairs lay on or near the beads. Their reading replaces the lone warrior chief with an elite of both sexes, where the dividing line was class rather than gender.
The mound also holds mass graves, five in all, each containing from about twenty to more than fifty bodies. One pit held 53 women, most of them aged about 15 to 30. Another group of 39 men and women showed signs of violent death, including partial decapitation, fractures and arrow points. Archaeologists interpret many of these burials as sacrifices, but who the victims were, where they came from and exactly what the ceremonies meant are still not fully understood.
Why was Cahokia abandoned?
Cahokia was abandoned gradually: the population began to fall after about 1200, and the city was largely empty by about 1350 to 1400. No single cause explains the decline, and archaeologists treat it as the result of several pressures acting together.
Political and social conflict is one strand. The palisade, rebuilt repeatedly, and changes in craft production and settlement around 1200 point to a society under strain. Drought and crop failure have also been proposed as stresses on a city that depended on maize.
Flooding is a third. In a 2015 study in the Proceedings of the National Academy of Sciences, Samuel Munoz, Jack Williams and colleagues analysed sediment cores from Horseshoe Lake near the city's centre and from Grassy Lake downstream. They found that Cahokia grew during a relatively dry, flood-free period from about 600 to 1200 CE, and that a major Mississippi flood around 1200 coincided with the beginning of the decline. The authors presented the flood as one destabilising factor alongside others, not as the whole explanation.
An older idea, the "wood overuse" hypothesis first proposed in 1993, held that Cahokians stripped the upland forests for fuel and building timber, causing erosion and local flooding in the creeks around the city. A 2021 study in Geoarchaeology based on work by Caitlin Rankin at Washington University in St. Louis tested this at a Mississippian mound on the Cahokia Creek floodplain. The ground surface beneath it stayed stable from the Mississippian period until industrial development in the mid-1800s, which gives little support to the hypothesis. The cause of abandonment remains open, and the current picture is multi-causal.
How does Cahokia compare with Mexico's great cities?
Cahokia is often compared with the cities of Mesoamerica because both built flat-topped platforms around plazas, but the differences are large. Teotihuacan was far older and larger and had declined centuries before Cahokia grew, and Mesoamerican pyramids were usually faced with stone, while Cahokia's were earth topped with timber buildings. Maize was first domesticated in Mexico, so crops and some ideas certainly moved north over many centuries; whether there was any more direct contact is debated. For the wider picture, see pyramids around the world and the disputed claims.
Billy Carson's reading
Billy Carson has not published a dedicated talk or episode on Cahokia, so this article does not attribute a specific position on the site to him. His broader reading of the ancient Americas runs through his work on Teotihuacan and on Thoth, where he argues for links between ancient Mexico and Egypt and treats recurring pyramid forms, solar alignments and sacred geometry as echoes of knowledge shared across early civilisations. In his interpretation, sites around the world draw on a common, older source, a view he connects to the Anunnaki of the Sumerian texts.
That is his interpretation, not the archaeological consensus, and at Cahokia the record is unambiguous on one point: the city, its mounds, its calendar circles and its burials were the work of Native Americans of the Mississippian culture. Readers who want to set Cahokia beside Billy's wider argument can start with the companion pieces on Teotihuacan and on pyramids around the world, and with the Anunnaki and Sumer topic hub.
Watch, read and go deeper
The Megalithic Mysteries series on 4BK TV looks at the great monuments of the ancient world and the questions they raise. For a related subject in the same region, the 4biddenknowledge archive includes a news post on the sale of Missouri's Picture Cave, a site whose paintings scholars associate with the early Mississippian world; read the dedicated academic study listed below for the archaeology. The Anunnaki topic hub collects Billy Carson's work on ancient origins, and the companion guides to Teotihuacan, Chichén Itzá and Stonehenge cover the other sky-aligned sites mentioned here.
Frequently asked questions
How old is Cahokia?
People lived in the American Bottom long before the city, but Cahokia's rapid growth into a city began around 1050 CE. Its peak population came between about 1050 and 1150, and the city was largely abandoned by about 1350 to 1400. The earliest woodhenge circles are older, from about 900 CE.
How many people lived at Cahokia?
Estimates for the peak, around 1050 to 1150 CE, are commonly given as 10,000 to 20,000 people. These figures are reconstructions from excavated houses and settlement density rather than counts.
Is Monks Mound bigger than the Great Pyramid?
Monks Mound's base, between 5 and 6 hectares, is comparable to the Great Pyramid of Giza's footprint. It is much lower, about 30 metres against the Great Pyramid's original height of roughly 146 metres, and it is built of earth rather than stone. It is the largest prehistoric earthen structure in the Americas.
Was Woodhenge connected to Stonehenge?
No. Both mark the sun's turning points, but they were built thousands of years apart on different continents by unrelated peoples. Solar calendars of posts or stones developed independently in many cultures because the sunrise positions at the solstices and equinoxes are visible to anyone who watches the horizon over a year.
Why was Cahokia abandoned?
Its population fell after about 1200 and the city was largely empty by about 1350 to 1400. Proposed causes include political and social conflict, drought, and a major Mississippi flood around 1200 identified in lake sediments. Most archaeologists see the decline as multi-causal, and the question is still open.
Sources and further reading
- UNESCO World Heritage Centre, "Cahokia Mounds State Historic Site" (inscribed 1982)
- Timothy R. Pauketat, Cahokia: Ancient America's Great City on the Mississippi (Viking, 2009)
- Melvin L. Fowler, Jerome Rose, Barbara Vander Leest and Steven R. Ahler, The Mound 72 Area: Dedicated and Sacred Space in Early Cahokia (Illinois State Museum, 1999)
- Thomas Emerson, Kristin Hedman, Eve Hargrave, Dawn Cobb and Andrew Thompson, "Paradigms Lost: Reconfiguring Cahokia's Mound 72 Beaded Burial," American Antiquity 81 (2016)
- Samuel Munoz, Jack Williams and colleagues, study of Horseshoe Lake flood records and Cahokia, Proceedings of the National Academy of Sciences (2015)
- Caitlin Rankin and colleagues, study of the wood-overuse hypothesis at Cahokia, Geoarchaeology (2021)
- Carol Diaz-Granados, James R. Duncan and F. Kent Reilly III, eds., Picture Cave: Unraveling the Mysteries of the Mississippian Cosmos (University of Texas Press, 2015)
- Cyrus Thomas, Report on the Mound Explorations of the Bureau of Ethnology (Smithsonian Institution, 1894)
