SOCIETY × ENVIRONMENT

The Mounds of Cahokia

~1050 CE

History · Middle Ages · Holocene · Meghalayan

Around 1050 CE, on the Mississippi floodplain across from modern St. Louis, a planned city rose almost at once: earthen pyramids around great plazas, the largest, Monks Mound, bigger at the base than Giza's pyramid, feeding on maize fields and drawing thousands of people. Cahokia flourished during a rare lull in great floods; when the droughts came from 1150 and the river's floods returned after 1200, the city walled itself in, emptied by half, and by 1350 the region was silent.

Why it matters

North America had its metropolis five centuries before Europeans arrived, and its trajectory is now read with the full toolkit, tree rings, flood sediments, even molecular traces of its inhabitants in lake mud. Cahokia joins the Maya and Angkor in the modern ledger of climate-stressed cities, and corrects a durable blind spot: the lands north of Mexico were never a wilderness waiting for history to start.

Dating & uncertainty

Central Cahokia was built abruptly around 1050 CE, during one of the wettest half-centuries of the millennium; decline set in from about 1150 amid drought, Mississippi floods and a hastily raised palisade of twenty thousand logs, and the region was abandoned by about 1350. A molecular census, fecal markers in lake sediments, now tracks its population rising and falling.

Sources

1. Muñoz et al. (2015), PNAS · Cahokia's emergence and decline coincided with shifts of flood frequency on the Mississippi Riverdoi:10.1073/pnas.1501904112
2. White et al. (2019), PNAS · Fecal stanols show simultaneous flooding and seasonal precipitation change correlate with Cahokia's population declinedoi:10.1073/pnas.1809400116
3. Benson, Pauketat & Cook (2009), American Antiquity · Cahokia's boom and bust in the context of climate changedoi:10.1017/s000273160004871x

Our species’ history as one day

23:55:324 min 28 s before midnight

if the 315,000 years of Homo sapiens were compressed into a single day