Illinois 200: Cahokia Mounds was 'America's first city'

A gaggle of rambunctious fifth-graders scrambled to the top of the 100-foot-high Monks Mound to get a great view of the Gateway Arch in downtown St. Louis and burn off energy at the end of their class field trip to the Cahokia Mounds State Historic Site.

Before climbing Monks Mound, the Gardner Elementary students from Waterloo, Illinois, toured the historic site's spacious interpretive center in Collinsville, Illinois, and learned how Native Americans based at the mounds conducted trade with people in other regions, including the Great Lakes for copper and the Gulf of Mexico for seashells.

"People from around the world come here to see the Cahokia Mounds, and it's right in our backyard," said Amy Wagenknecht, one of the students' teachers.

The students were among the estimated 300,000 people who visit the state historic site each year.

Monks Mound was built by Native Americans who are now known as members of the Mississippian culture. It is the largest pre-Columbian, earthen structure in all of North and South America, said Bill Iseminger, the assistant site manager who has worked at Cahokia Mounds since 1971.

It also is one of the 80 earthen mounds remaining in the area, with 70 of the mounds protected within the Cahokia Mounds State Historic Site, which encompasses 2,200 acres. There originally were 120 mounds at the site.

At the height of the Cahokia Mounds, an estimated 10,000 to 20,000 American Indians lived at the site, and perhaps twice as many lived in the region, Iseminger said.

Cahokia was the largest prehistoric American Indian settlement north of Mexico. It's known as "America's first city," and it is believed to have had a population larger than London in 1250.

Archaeologists are not sure why the Mississippians formed this major settlement around 1000 to 1050, and they don't know why the site was abandoned by 1400, Iseminger said.

"The urban nature of Cahokia is what intrigues a lot of archaeologists and historians; trying to understand how it began and how it ended and that middle period is something we're all constantly trying to unravel," Iseminger said. "We don't know what they called themselves or this place. It's not really a tribe; it's an urban area."

Archaeologists have raised questions about why the city rose from the Mississippi River flood plain near present-day St. Louis: Was it a powerful leader? Was a new religion developing? Was it inspired by a supernova seen worldwide in 1054?

Iseminger said a combination of motivations likely caused the Cahokia site to be abandoned.

"They probably depleted most of the natural resources in the area," Iseminger said.

Other possible causes include: a few bad leaders running the city; reduced crop production caused by extended droughts and cooling temperatures; flooding; nutritional problems from an overdependence on a diet of corn; a contagious disease could have spread with so many people living in proximity; and a gradual breakdown of the ruling system with some challenging the authorities.

"Where they went or what tribes they became is not clear," Iseminger said.

In the 1800s, the mounds were named after the Cahokia tribe that lived in the area when European settlers arrived. But that tribe had moved into this area long after the mounds site had been abandoned.

• Mike Koziatek of the Belleville News-Democrat can be reached at or on Twitter at @MikeKoziatekBND. Illinois 200 is produced as a project of the Illinois Press Association and the Illinois Associated Press Media Editors. Find previous stories at

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Visitors at the Cahokia Mounds Interpretive Center see how archaeologists believe Native Americans lived at the site. Belleville News-Democrat
For 47 years, Bill Iseminger has been assistant manager for the Cahokia Mounds State Historic Site. It was his first job after he graduated with his master's in anthropology from Southern University of Illinois Carbondale in 1971. Belleville News-Democrat

If you go

Cahokia Mounds State Historic Site attracts about 300,000 visitors annually.

• Location: Collinsville, Illinois

• Hours: 9 a.m. to 5 p.m. Wednesday through Sunday during winter. The site is usually open seven days a week during the summer.

• Contact: (618) 346-5160, or the Facebook page called Cahokia Mounds World Heritage Site.

• Groups: Download a group reservation form from the mounds' website and email it to

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