Cahokia Mounds

Around 1050, a city rose on the Mississippi floodplain near modern St. Louis that had no European witness at either end: Cahokia held an estimated ten to twenty thousand people at its peak, covered a territory of dozens of platform, conical, and ridgetop mounds, and anchored a Mississippian world that stretched across the Midwest and Southeast. Monks Mound, its center, is a hundred-foot earthen platform mound, the largest earthwork in North America, built a shovel-load at a time without draft animals or metal tools. East of it stands the reconstructed Woodhenge, a ring of cedar posts whose gaps frame the solstice sunrises, and archaeology at Mound 72 revealed mass burials and a ruler laid on a bed of some twenty thousand shell beads. By the time Europeans arrived the city was empty; why it emptied is one of North American archaeology's standing questions.

Today the site is free and open, administered by the state, with the UNESCO inscription from 1982 and an interpretive center coming back to full strength after years of building repairs; the lobby reopened to visitors in 2026 while exhibits are rebuilt. The experience is mostly outdoors: climb Monks Mound's steps, walk the palisade lines and mound field, and read the site the way the city would have been read, as public architecture. Cahokia matters to this library as the monumental end of the same mound-building tradition whose living descendants keep other sites sacred today.

Visiting

Cahokia Mounds State Historic Site is run by the Illinois historic sites division: grounds open daily dawn to dusk, free; the interpretive center lobby is open reduced hours during the exhibit renovation.

Photo: [Antony-22](https://commons.wikimedia.org/wiki/File:Cahokia_2025e.jpg), Wikimedia Commons, CC BY-SA 4.0.