We’re all fascinated by ancient lost cities like Machu Pichu, Petra, and Troy, but did you know the United States has them, too? In addition to Mesa Verde in Colorado, the midwest has its own, created by Native Americans. In the December 7th episode of Overheard at National Geographic, host Amy Briggs looks at this historic site, and the work being done to preserve and study it in “Descendants of Cahokia.”

(Richard Schlecht/National Geographic Image Collection)

(Richard Schlecht/National Geographic Image Collection)

Cahokia was an ancient American Indian city near present-day St. Louis, across the Mississippi River in southwest Illinois. Starting around 500 A.D., the Osage ancestors migrated across middle America and made a home along the Mississippi River. According to one of the special guests, archeologist Tim Pauketat, the area would’ve been appealing for several reasons. It’s where the Missouri River meets the Mississippi, making it an easy spot for trade, and the landscape is dotted with caves, which symbolize a portal into the underworld. A lot of what researchers know about the area comes from cave paintings and shrines near cave access points.

Around 1050 A.D., Cahokia was the largest American Indian city north of the Rio Grande long before European settlers arrived. The climate had become warmer, and corn was a fertile crop in the region by then. Cahokia went from a big village of around 3,000 people to a major city of over 10,000 people. There’s evidence that people moved to Cahokia as the culture spread along the Mississippi River, making the city a melting pot of Indigenous cultures and language. By the 12th century, the population is estimated to have been around 20,000 residents.

Native Americans started building mounds more than 5,000 years ago, but the mounds in Cahokia were bigger and grander than anywhere else. If you were there in its heyday, giant mounds would’ve been the defining feature of the landscape. But today, many of them are gone. Cahokia was abandoned just a few hundred years after the empire expanded. When French settlers built St. Louis, the region was nicknamed “Mound City” due to many Cahokia remnants. Many of the mounds were torn down by the end of the 19th century, using the dirt for railroad construction and leveling the region for the 1904 world’s fair. This includes a mound that was known to the settlers as “Big Mound,” which was 30 feet tall and about the length of a football field.

One of the surviving mounds from Cahokia is known as “Sugarloaf Mound” nicknamed because its shape resembled the way sugar used to be transported. It’s in a southern section of St. Louis between the Mississippi River and Interstate 55. The 40-foot-tall mound has two tiers, with a house erected on the lower tier and stairs installed leading to the top tier. It’s surrounded by a chain-link fence and a sign that warns trespassers to stay out. It’s now marked with the seal of the Osage Nation, but that wasn’t always the case.

Andrea Hunter is an archeologist and a member of the Osage Nation who directs the tribe’s historic preservation office. In this podcast episode, she recounts the story of how she helped return Sugarloaf Mound to her people, which had been privately owned since the 1920s. In 2008, the owners decided to sell the mound’s upper tier and she helped convince the Osage Nation to buy it for around $250,000. Once purchased, the house on the top tier was removed and Andrea could begin exploring the mound’s mysteries.

Many Native American mounds are sacred burial sites, so digging isn’t an option. Ground-penetrating radar was used and what’s been found so far is a three-foot-wide anomaly about a foot-and-a-half below the surface. Nobody knows for sure what it is, but the leading theory is that it’s the remains of a huge fire pit atop the mound. From the top of Sugarloaf Mouna, Andrea can see another surviving big mound, known as “Monks Mound,” and the vantage point from Sugarloaf Mound offers a view of the river that would be a blind spot from Monks Mound. The theory is that Sugarloaf Mound may have been an outpost that used smoke to communicate the arrival of boats on the river to central Cahokia. Andrea hopes to go back with stronger instruments to learn more about what’s inside Sugarloaf Mound. Andrea is also looking for more Indigenous sites that can be procured back to the Osage Nation.

Cahokia Mounds is an Illinois state heritage site and visitors can climb the 156 steps to the top of Monks Mound, from which they can see other mounds and get a sense of how big Cahokia was. Monks Mound looks like a couple of wide rectangles stacked on top of each other like a step pyramid. It’s one-hundred feet tall with a footprint larger than the Great Pyramid of Giza, bigger than any other human-made earthen structure in North America. Time has eroded it, but when built, it would’ve had sharp 45-degree angle sides and would’ve been kept free of grass and weeds. Monks Mound is believed to have been a ritual site to mark lunar cycles and make offerings for rain.

In 2021, another important Cahokia site went up for sale, but this time, Andrea lost the bidding war. Picture Cave is on private property 60 miles west of St. Louis that has been studied by husband and wife anthropologist team Jim Duncan and Carol Diaz-Granados, who also join this episode to talk about their findings. Rock art was discovered inside the cave around 1990, and due to Carol’s experience with rock art, she asked to see the evidence. Getting in isn’t easy, with a narrow passage that requires laying down on the ground and sliding, followed by a dark descent into a cavern with around 400 cave drawings. They depict humans, animals, and fantastical creatures. Chemical dating shows that the cave paintings are a thousand years old, dating back to around the time Cahokia was born. Carol and Jim worked with Osage elders to document the cave paintings, and when it went up for sale, an anonymous buyer paid more than two million dollars for the cave and surrounding land.

The story of Picture Cave may not have ended the way Andrea wanted it to, but not all stories end on a sour note. A Missouri landowner heard about the story and donated 20 acres of their land, on which they had found mounds, which are now back in the hands of the Osage Nation. Andrea is also in talks to recover 80 acres in another part of Missouri to help keep the Osage legacy alive. Her dream is to build an educational center at Sugarloaf Mound to educate people about the culture and religion of the region around the time of Cahokia.

Click here to listen to Overheard at National Geographic.