This paper studies the July 1995 heat wave in which over 700 Chicago residents, most of them old and impoverished, died. It presents a ‘social autopsy’ of the disaster that goes beyond natural factors to uncover the institutional forces that made the urban environment suddenly so lethal, highlighting four key conditions: (1) the increase in the number and proportion of people living alone, including seniors who outlive or become estranged from their social networks; (2) the fear of crime and the use of social withdrawal and reclusion as survival strategies; (3) the simultaneous degradation and fortification of urban public space, particularly in segregated neighborhoods that have lost major commercial establishments and other attractions that entice people out of their homes; (4) the political dysfunctions stemming from social service programs that treat citizens as consumers in a market for public goods despite a growing population of residents who lack access to the information and network ties necessary for such ‘smart shopping’ for city support. Conclusions and recommendations are discussed.