In the summer of 1995, a blistering heat wave settled over Chicago for three days. It killed 739 people, making it one of the most unexpectedly lethal disasters in modern American history. No statistical models of the heat wave predicted such a high death toll. Researchers in the American Journal of Public Health reported that their analysis “failed to detect relationships between the weather and mortality that would explain what happened.”
Just as mysterious as the number of fatalities was the way they were distributed across the city. Several of the most deadly areas were entirely black and disproportionately poor, but so were three of the least deadly. Adjacent areas that looked alike—like Englewood and Auburn Gresham, two hyper-segregated black South Side neighborhoods with high poverty and crime—suffered vastly different effects.
Scientists who study urban breakdowns like this usually focus on hard-line infrastructure: electrical grids, transit networks, communications systems, water lines, and the like. And to be sure, Chicago’s aging infrastructure was woefully equipped for extreme heat. The power grid failed, leaving tens of thousands without air conditioning. Roads buckled and drawbridges locked, leading to gridlock and long ambulance response times. But those failures blanketed the entire city; they didn’t explain the patchwork death toll.
As a young sociologist who grew up in Chicago, I wanted to figure out why the heat wave killed who it did, where it did. So I set out to examine those pairs of “neighboring neighborhoods” that should have fared similarly but didn’t.