Abstract
Abstract We study the effects of European immigration to the U.S. during the Age of Mass Migration (1850–1920) on economic prosperity. Exploiting cross-county variation in immigration that arises from the interaction of fluctuations in aggregate immigrant flows and of the gradual expansion of the railway network, we find that counties with more historical immigration have higher income, less poverty, less unemployment, higher rates of urbanization, and greater educational attainment today. The long-run effects seem to capture the persistence of short-run benefits, including greater industrialization, increased agricultural productivity, and more innovation.