The word ‘urban’ is now commonly used to characterize the unusual, amorphous, and sprawling three-part complex of monuments, water features, and pole-and-thatch buildings known as Cahokia. Besides its tripartite spatiality, Cahokia was anomalous in other ways. It arose rapidly, was built in a watery landscape, and was a relatively short-term phenomenon. To understand these anomalous qualities, we focus on three archaeologically isolatable, short-term episodes of Cahokian history (ad 1050, 1125 ± 25, and 1200) and review the development of both central precincts and rural localities. We suggest that Cahokia’s vitality was a function of its region-wide incorporation of other-than-human powers, especially as related to water, while its diminution was at least partly a function of the general absence of urban infrastructure, especially as related to water.