Long before Columbus reached the Americas, Cahokia was the biggest, most cosmopolitan city north of Mexico. Yet by 1350 it had been deserted by its native inhabitants the Mississippians – and no one is sure why

In its prime, about four centuries before Columbus stumbled on to the western hemisphere, Cahokia was a prosperous pre-American city with a population similar to London’s.

Located in southern Illinois, eight miles from present-day St Louis, it was probably the largest North American city north of Mexico at that time. It had been built by the Mississippians, a group of Native Americans who occupied much of the present-day south-eastern United States, from the Mississippi river to the shores of the Atlantic.

Cahokia was a sophisticated and cosmopolitan city for its time. Yet its history is virtually unknown by most Americans and present-day Illinoisans. It is one of many stories that have been bypassed in favour of the shopworn narrative – reinforced in literature and a century of American cinema – of Native Americans as backward and primitive.

“A lot of the world is still relating in terms of cowboys and Indians, and feathers and teepees,” says Thomas Emerson, professor of anthropology at the University of Illinois. “But in AD1000, from the beginning, [a city is] laid on a specific plan. It doesn’t grow into a plan, it starts as a plan. And they created the most massive earthen mound in North America. Where does that come from?”

Its mix of people made Cahokia like an early-day Manhattan, drawing residents from throughout the Mississippian-controlled region: the Natchez, the Pensacola, the Choctaw, the Ofo. Archaeologists conducting strontium tests on the teeth of buried remains have found a third of the population was “not from Cahokia, but somewhere else”, according to Emerson, who is director of the Illinois State Archaeological Survey. “And that’s throughout the entire sequence [of Cahokia’s existence.]”

The Native Americans at Cahokia farmed, traded and hunted. They were also early urban planners, who used astronomical alignments to lay out a low-scale metropolis of 10-20,000 people, featuring a town centre with broad public plazas and key buildings set atop vast, hand-built earthen mounds. The largest of these mounds was 100 feet tall and covered 14 acres – and still exists today.

But rather than developing, like London, into a modern metropolis, Cahokia is more like the fabled lost continent of Atlantis. Having become a major population centre around AD1050, by 1350 it was largely abandoned by its people – and no one is sure why. Neither war, disease, nor European conquest drove Cahokia’s residents from their homes. Indeed, the first white man to reach these lands, Spanish explorer Hernando de Soto, didn’t do so until 1540.

The mound-building Mississippians dominated a great portion of the eastern half of the present-day United States between 1000 and 1500. Many of their villages were established near trade routes or sources of water and food – but Cahokia was different.

Though rich in timber, deer and fish from the Missouri and Mississippi rivers, the land was flood-prone – so why build there? According to Emerson, the most likely explanation is that Cahokia was planned and constructed to double as a “pilgrimage city”, where all Mississippians could gather for religious events.

“It might’ve been a good area to explore but not so good to live in,” Emerson says. “But then something changed around AD1000, and it becomes this major centre. Most of the change has nothing to do with the economy, but what we broadly call religion.”

Not unlike postwar America suburbs such as Levittown, Pennsylvania or Park Forest, Illinois, the Mississippians planned and built Cahokia – having successfully predicted that a population would flock to it. They created a city that was between six and nine square miles in area, with 120 earthen mounds inside its rough borders. The mound-building would have been backbreaking work, with the Mississippians digging up, hauling and stacking 55 million cubic feet over the course of a few decades, using no more than woven baskets to transport all that earth.

Cahokia’s largest mound (later called Monk’s Mound, after the French Trappists who tended to its terraced gardens in the 1800s) was the site of a sizeable building in which Cahokia’s political and spiritual leaders met, according to archaeologists. Surrounded by a wooden palisade almost two miles in circumference, the town centre was where residents, pilgrims and leaders worshipped and held ceremonies.

Most of the Mississippians lived on the other side of the palisade in rectangular, single-room homes about 15 ft long and 12 ft wide, with wooden-post walls covered with mats and a thatched roof. Far from being a collection of villages or campsites, the homes were linked by courtyards and pathways, forming shared physical connections not unlike contemporary streets. The habitants even plotted an east-west road that is essentially the route from the area to St Louis today.

‘Its decline is a mystery’

During its prime, Cahokia would have bustled with activity. Men hunted, grew and stored corn, and cleared trees for construction. Women tended to the fields and homes, made pottery, wove mats and fabrics, often performing work and social activity in the small courtyards and gardens outside each grouping of homes.

Sacred meetings and ceremonies – the city’s purpose – took place on the plazas and in buildings inside the palisade. “There was a belief that what went on on Earth also went on in the spirit world, and vice versa,” says James Brown, a professor emeritus of archaeology at Northwestern University. “So once you went inside these sacred protocols, everything had to be very precise.”

The Mississippians oriented Cahokia’s centre in a true east-west fashion, using site lines and the positions of the sun, moon and stars to determine direction accurately. West of Monk’s Mound, a circle of tall posts used the position of the rising sun to mark the summer and winter solstices and the spring and fall equinoxes. The posts were re-erected and dubbed Woodhenge by archaeologists who began researching the area in 1961.

Excavations since the 60s have yielded fascinating information about this ancient city. Scholars have found artistic stone and ceramic figurines; Brown was part of team that discovered a small copper workshop adjacent to the base of one of the mounds. “Inside was a fireplace with coals, where copper could be pounded out and annealed,” he says. “They pounded it out, heated it to allow the crystals in the cooper to realign, and when they quenched this in water, you’d have something that resembled an ornament, a bead.”

Archaeological work has also discovered a mound containing mass burials. While the extent of it is debated, it appears the Mississippians may have conducted ritual human sacrifices, judging by what appears to be hundreds of people, mostly young women, buried in these mass graves. Some were likely strangled; others possibly died of bloodletting. Four men were found with their heads and hands cut off; another burial pit had mostly males who had been clubbed to death.

The people of Cahokia themselves may have both doled out and received a lot of this violence, since researchers have found no specific evidence of warfare or invasion from outsiders. Emerson says he has excavated other Native American sites that were filled with arrowheads left behind by war; by comparison, at Cahokia there were almost none. “It’s interesting,” he adds. “At Cahokia the danger is from the people on top; not other people [from other tribes or locations] attacking you.”

But William Iseminger, archaeologist and assistant manager at Cahokia Mounds, points out there must have been some continuing threat to the city, whether from local or distant sources, that necessitated it being built and rebuilt four times between 1175 and 1275. “Perhaps they never were attacked, but the threat was there and the leaders felt the need to expend a tremendous amount of time, labour and material to protect the central ceremonial precinct.”

The story of Cahokia’s decline and eventual end is a mystery. After reaching its population height in about 1100, the population shrinks and then vanishes by 1350. Perhaps they had exhausted the land’s resources, as some scholars theorise, or were the victims of political and social unrest, climate change, or extended droughts. Whatever, the Mississippians simply walked away and Cahokia gradually was abandoned.

Tales of Cahokia don’t even show up in Native American folklore and oral histories, Emerson says. “Apparently what happened in Cahokia left a bad taste in people’s minds.” The earth and the mounds provide the only narrative.

As archaeological studies here continue, Monk’s Mound is now the centrepiece of the 3.5 square-mile Cahokia Mounds State Historic Site (a Unesco World Heritage Site since 1982), which includes 2,200 acres of land, 72 surviving mounds, and a museum. The US National Park Service is considering whether to take the area and nearby surviving mounds under its wing.

Federal designation could bring Cahokia additional recognition and tourism. Currently about 250,000 people visit the site every year; by comparison, the rather more modern, Eero Saarinen-designed Gateway Arch in St Louis attracts four million visitors annually.

“Cahokia is definitely an underplayed story,” Brown says. “You’d have to go to the valley of Mexico to see anything comparable to this place. It’s a total orphan – a lost city in every sense.”