Fears of immigrants as a threat to public health have a long and sordid history. At the turn of the 20th century, when immigrants made up one-third of the population in crowded American cities, contemporaries blamed high urban mortality rates on the newest arrivals. We evaluate how the implementation of country-specific immigration quotas in the 1920s affected urban health. Cities with larger quota-induced reductions in immigration experienced a persistent decline in mortality rates, driven by a reduction in deaths from infectious diseases. The unfavourable living conditions immigrants endured explains the majority of the effect as quotas reduced residential crowding and mortality declines were largest in cities where immigrants resided in more crowded conditions and where public health resources were stretched thinnest.

During the 1918–1919 influenza pandemic, many local authorities made the controversial decision to close schools. We use newly digitized data from newspaper archives on the length of school closures for 165 large U.S. cities during the 1918–1919 flu pandemic to assess the long-run consequences of closing schools on children. We find that the closures had no detectable impact on children's school attendance in 1920, nor on their educational attainment and adult labor market outcomes in 1940. We highlight important differences between the 1918–1919 and COVID-19 pandemics and caution against extrapolating from our null effects to modern-day settings.