Closing Ranks: Organized Labor and Immigration

This paper shows that immigration fostered the emergence of American organized labor. I digitize archival records to assemble the first county-level dataset on historical U.S. unionization and use a shift-share instrument to isolate plausibly exogenous labor supply shocks induced by immigration, between 1900 and 1920. Counties with higher immigration experienced increases in union presence and membership. These effects were more pronounced among skilled workers, particularly in counties more exposed to immigrant labor competition, and in areas with more negative attitudes toward immigrants. The evidence is consistent with existing workers unionizing in response to immigration, driven by economic and social motivations.