Monks Mound at Cahokia built in decades, not 250 years as previously thought

By studying plant seeds and spores in the soil used to construct Monk’s Mound, the largest prehistoric earthen structure in North America, archaeologists have determined that it was not built over the course of 250 years, as previously thought, but in a fraction of that time.

Monk’s Mound is in the ruins of the ancient Native American city of Cahokia in the U.S. state of Illinois. At its height, about 1,000 years ago, Cahokia was home to as many as 15,000 people. The mound was a series of rectangular terraces that reached 10 stories or 30 meters (100 feet) in height, and the area of its base was larger than the Empire State Building in New York City. The structure had a large public building at is apex, perhaps a temple.

There are many other mounds at the site, but Monk’s Mount towers over them. It was named after Trappist monks who lived for a time on a nearby mound.