blog entry about the rise of Cahokia, the largest pre-Columbian settlement in North America, and the stresses and compensations of living in that extraordinary city. My entry did not, however, address the reasons for the city-state's decline, which began just a century after Cahokia's founding, in 1150 CE. Research for another project has introduced me to several articles which provide reasons for Cahokia's eventual disappearance (except as a cluster of mounds and a museum). One of the principal causes for the decline, according to Timothy Pauketat, Larry Beacon, and Edward Cook, was environmental: a series of droughts that afflicted Indian communities in the Midwest in the 12th and 13th centuries, leading to the abandonment of the farming villages that supplied Cahokia with food. The city was already suffering from resource depletion and shortage: the American Bottom, fertile though its soils were, had a natural shortage of mineral resources, and the construction of Cahokia and its satellite communities produced severe shortages of firewood by 1150.
To these environmental stresses we may add a cultural one: Cahokia's religious and social elite began pursuing individual display and military glory in the 12th and 13th centuries, a shift from more communally-oriented behavior that is demonstrated in the archaeological record by increased burials of exotic, even unique, "prestige goods" like copper jewelry and shell cups, and by the abandonment of mound-building in favor of constructing defensive palisades. This increased individualism undermined the elite's authority as mediators for the community, while increased drought and resource depletion made it clear that both the spiritual and material worlds were angry with the priest-aristocrats. By the middle of the 12th century Cahokia had lost about half of its peak population, and the rest of the city's inhabitants had dispersed by the early 1300s, just in time for the Little Ice Age to shut down the other Mississippian settlements in the Midwest.
Sources: Larry Benson, Timothy Pauketat, and Edward Cook, "Cahokia's Boom and Bust in the Context of Climate Change," American Antiquity 74 (2009): 467-83; Mary Beth Trubitt, "Mound Building and Prestige Goods Exchange: Changing Strategies in the Cahokia Chiefdom," ibid, 65 (2000): 669-690.