Cahokia

A city on the Mississippi

Cahokia grew up on a wide, fertile floodplain called the American Bottom, on the Illinois side of the Mississippi River, across from today's St. Louis. Rivers were highways: the Missouri and the Illinois join the Mississippi nearby, and the Ohio joins it a little to the south, so people and goods could travel in every direction.

At its peak, roughly 1050 to 1200, archaeologists estimate 10,000 to 20,000 people lived in the city, with more in nearby towns. Some estimates run higher. London around 1100 is usually estimated at about 15,000 to 20,000 people, so the two were in the same range. That's a comparison, not a ranking.

Cahokia was the largest center of what archaeologists call the Mississippian culture. The name "Cahokia" comes from a later Illinois-speaking group; the city's own name is not known.

Corn and earthen mounds

The city ran on farming, above all corn (maize), along with other crops, fishing and hunting. With that food, people had the time and labor to build big projects.

They built about 120 earthen mounds, basket load by basket load of soil. Some were flat-topped platforms for buildings, others were burial mounds. About 70 are still preserved.

The biggest is Monks Mound: about 100 feet (30 m) tall, with several terraces. It is the largest earthwork of its kind north of Mexico. (Its name comes from French monks who lived nearby in the 1800s, long after the city was empty.)

Leaders on top, a plaza below

Leaders lived on top of Monks Mound, where a large building stood. In front of it lay the Grand Plaza, a huge, flattened open space used for ceremonies and games such as chunkey, a game of rolling a stone disk and throwing spears after it.

Later, in the 1100s, a wooden wall called a stockade (or palisade) was built around the central area, and it was rebuilt several times.

Why did people leave?

By about 1350, the city was mostly empty. Historians and archaeologists still debate why. Ideas include:

• Floods on the river floodplain
• Drought and failing harvests
• War or conflict, which the stockade hints at
• Politics: leaders losing power, or groups splitting up

It was probably more than one cause, and some research suggests people left gradually over many years rather than all at once.

Try it yourself

Find Cahokia Mounds State Historic Site on a map, just east of St. Louis. Switch to satellite view and look for Monks Mound: the big terraced, tree-edged hill with the open Grand Plaza to its south.

Good to know

• Population estimates vary: UNESCO and the National Park Service give 10,000 to 20,000 at the peak (about 1050 to 1200); some estimates reach 40,000, and the Illinois State Archaeological Survey cites a regional population over 50,000.
• London around 1100 is usually estimated at roughly 15,000 to 20,000, so "about as big as London" is a comparison, not a ranking.
• About 120 mounds were built; around 70 are preserved.
• Monks Mound is about 30 m (100 ft) tall. UNESCO calls it the largest prehistoric earthwork in the Americas; "largest of its kind north of Mexico" is the safer claim.
• The stockade was built in the 1100s and rebuilt several times.
• Causes of the decline are debated (floods, drought, resource strain, conflict, political change), and some research argues the population thinned gradually.
• Several Siouan-speaking peoples (for example the Osage) are among possible descendant nations; tying Cahokia to one specific modern nation is debated.
• "Cahokia" comes from a later Illinois-speaking group, not the city's original name, which is unknown.