Did the expansion of compulsory education create a national identity? In this paper, I explore this question within the context of the United States during the Age of Mass Migration (1850-1930). Using the expansion of compulsory schooling laws, I leverage both regression discontinuity and difference-in-differences identification strategies combined with individual-level data on the entire population of immigrants residing in the United States in 1930 to estimate the causal effect of mass education on assimilation. The results provide evidence of a precise null effect of education on national identity formation in the United States. Further tests provide evidence that the lack of this effect resulted from mass implementation failures. These results imply a limited scope for mass schooling to explain the assimilation of the United States’s diverse population in addition to highlighting the importance of understanding why states fail to build national identity.