This paper studies nation-building. We explore the role of statesponsored education in the adoption of a common language and the formation of a national identity in a fragmented society. At the time of the French Revolution, only ten percent of the population spoke the French language in France. We digitize a novel municipality-level dataset on spoken languages to document the process of homogenization in the nineteenth century. Using a regression discontinuity design, we demonstrate that state-sponsored education brought about the homogenization of language. Then, we study the geographical origins of the French language and the heterogeneous effects of schools. We find that elites were an important driver of homogenization. Finally, we document a persistent impact of nation-building on national identity and preferences for political centralization, with increased participation in the Resistance during World War II and votes against the 1969 referendum on regionalization.