In this paper we study the effect of violent crime on residential and firms location decisions and their implications for segregation in cities. We do so by proposing a new instrument to exogenously predict violent crime in city centers. We base our instrument on chemical and medical evidence that links local characteristics of the soil to lead poisoning and aggression. We show that the increase in violent crime between 1960 and 1990 due to lead poisoning moved almost 8 million people to the suburbs. Firms followed by leaving the city centers. We then show that the suburbanization process was characterized by “white flight”.