What are the origins of national identity? We investigate the success of propaganda as one the first nation-building policies conducted in the German lands around 1815. To elicit identity changes at the level of individuals we use data on first names across German cities and villages. To validate the approach of using first names, we show that soldiers with national names had a higher likelihood to be honored for bravery during the German-French War. Exploiting unanticipated border changes together with variation within the same families over time, i.e., family fixed effects, we find that parents in treated cities responded by choosing national (rather than ruler) first names for their children. We do not find a corresponding increase in villages suggesting that national identity was more prevalent among the urban population, in particular the elite, during this period. •First nation-building policies in German lands in 1815 were successful.•Change in parents’ decision on first names used as proxy for change in social identity.•Unanticipated border changes allow constructing treatment and control group.•Exploiting family fixed effects supports causal identification at individual level.•National identity was more prevalent among urban elites.