Dichlorodiphenyltrichloroethane, or DDT, may be the most famous—and infamous—pesticide in existence. The U.S. banned it nearly half a century ago, in 1972. But its story persists. When the New York Times reported the discovery of a lost Nazi pesticide last month, it compared it to DDT. This summer’s news stories on the U.S. bird population’s decline—down nearly a third from 1970s levels—featured reminders of the 1960s discovery of DDT’s harm to wildlife. A stream of news reports on the dangers of neonicotinoids, our latest pesticides, invokes DDT’s history as a warning against adopting new chemicals too quickly. In a handful of poverty-stricken parts of the world, DDT is still dusted and sprayed to kill disease-carrying mosquitoes and other bugs. In the U.S., by contrast, DDT has evolved from a material technology to a morality tale, one that tells us how to use the past to think about the present. This talk will cover how and why this morality tale took shape, discuss the cultural and political functions it has served over time, and show how shedding light on the story’s errors and omissions can expand our knowledge of the U.S. public’s understanding of science since the Second World War.