Immigration and Child Mortality during the Age of Mass Migration

In the late nineteenth century, Americans feared that crowded immigrant neighborhoods were spreading disease through industrial cities. We study this claim using newly constructed town-level panel data from Massachusetts, 1860 to 1915, a setting uniquely suited to this exercise because its early vital registration system allows consistent measurement of mortality before national registration became widespread. Using a shift-share instrumental variable strategy based on historical settlement patterns, we estimate the effect of local exposure to immigration on mortality. The relevant question is not whether immigrant families themselves experienced higher mortality, but whether immigration altered the local disease environment more broadly. We find that increases in the foreign-born share significantly raised infant and child mortality, with the infant effect falling disproportionately on the post-neonatal period. Mechanical changes in the composition of births by parent nativity account for only a portion of the estimated effect, implying that the results are not driven primarily by higher mortality among immigrant births. Instead, the evidence is consistent with increased exposure to immigrants, communicable disease, and spillovers to children of native-born parents. These findings highlight immigration as one factor shaping the mortality transition in crowded high-mortality environments.