Cahokia, Illinois
Native American oral history and archaeological data alike suggest that farmers in parts of North America began abandoning major settlements such as Mesa Verde in Colorado and Cahokia in Illinois sometime after 1150. Now, a team led by archaeologist Robert Kelly of the University of Wyoming has studied this period using a previously assembled database of some 100,000 radiocarbon dates from across the United States. (See “Save the Dates.”) They used the dates to track pop