This paper analyzes the impact of migration on long-run economic development. In particular, I study the European migration to Argentina in the late nineteenth century. I use an instrumental variables approach to show that the historical population composition generated differences in current economic outcomes. The IV randomly assigns immigrants across counties by interacting two sources of exogenous variation: the availability of land for settlement and the arrival of Europeans over time. Areas with historically higher shares of European population currently have significantly higher per-capita GDP, higher education rates and a greater proportion of skilled workers. Moreover, I present results which suggest that industrialization and human capital were channels through which migration had long-run effects: counties with higher share of Europeans experienced more advanced levels of industrialization and higher literacy rates.