The onset of the Little Ice Age around 1350 may have played a decisive role in bringing down cities in the Mississippi River Valley. Angus Chen's article on NPR summarizes the most recent research on Cahokia, a once bustling city 10 miles east of present-day St. Louis. Researchers have been using calcite deposits at nearby Martin Lake, Indiana, to create a record of rainfall patterns stretching back hundreds of years. This record indicates that the Little Ice Age brought with it drought to Cahokia and other cities east of the Mississippi. Drought, in turn, undermined corn production and caused a subsistence crisis for residents of Cahokia. Despite this recent research, scholars are not convinced that climate alone brought down Mississippian societies. Rather, it may have exacerbated ongoing social and political tensions.