In this paper, we examine the economic and political effects of the breakup of East Prussia into what is today Poland, Russia and Lithuania. We explore the dissolution of imperial regions into the boundaries of modern states, adding new insights to the research on the imperial legacies. We expect that German imperial legacies in the form of advanced economic institutions, and specifically East Prussian legacies of nationalistic and conservative political preferences, persist in the territories of former East Prussia in Poland, Russia and Lithuania compared to neighboring regions in their respective countries. We find no pattern of persistence in former East Prussian territories of contemporary Poland, whereas East Prussian persistence appears to be robust in Lithuania. We find strong evidence for the comparative persistence of political preferences in the Kaliningrad region, whereas we observe no economic spillovers. Drawing evidence from West German electoral data in the aftermath of World War II, we find that the presence of East Prussian refugees is conducive to conservative and nationalist support in the FRG. Hence, the East Prussian legacy relates primarily to the persistence of political preferences and migrating agents.