Finding North America's lost medieval city

A thousand years ago, huge pyramids and earthen mounds stood where East St. Louis sprawls today in Southern Illinois. This majestic urban architecture towered over the swampy Mississippi River floodplains, blotting out the region's tiny villages. Beginning in the late 900s, word about the city spread throughout the southeast. Thousands of people visited for feasts and rituals, lured by the promise of a new kind of civilization. Many decided to stay.[...]Centuries later, Cahokia's meteoric rise and fall remain a mystery. It was booming in 1050, and by 1400 its population had disappeared, leaving behind a landscape completely geoengineered by human hands. Looking for clues about its history, archaeologists dig through the thick, wet, stubborn clay that Cahokians once used to construct their mounds. Buried beneath just a few feet of earth are millennia-old building foundations, trash pits, the cryptic remains of public rituals, and in some places, even, graves.To find out what happened to Cahokia, I joined an archaeological dig there in July. It was led by two archaeologists who specialize in Cahokian history, Sarah Baires of Eastern Connecticut State University and Melissa Baltus of University of Toledo. They were assisted by Ph.D. candidate Elizabeth Watts of Indiana University, Bloomington, and a class of tireless undergraduates with the Institute for Field Research. Together, they spent the summer opening three large trenches in what they thought would be a sleepy little residential neighborhood southwest of Monk's Mound.They were wrong.Fascinating. I had no idea native Americans built huge cities like this far north of - roughly - the current border between the US and Mexico.