The 20th century was marked by the intensification of the process of political change. Revolutions, two world wars, decolonization, the end of the Cold War, the collapse of the Soviet Union and the disappearances of the socialist bloc reorganized the balance of power in the world giving birth to several new States. The presented topics examine the cultural and political foundations on with the new States have been re-built and how they have attempted to construct new nation-states. The process is inevitably linked to a new interpretation of the past, often if not always centered on varying degrees of ethnocentrism. How does the relation to the imperial/colonial past evolve? To what extent does the new approach to historical past become an element of consolidation as well as of internal division in the newborn nations under construction? Also are analyzed the main trends that characterize the evolution of national historiography through the re-reading of national and imperial histories, their ethnicization and politicization, different traditions and new national myths in states.