Academic, scientific or professional interest: It is an unavoidable requirement for society to learn the historic background to understand better the present. It is necessary to reconstruct this history applying a scientific method to avoid explanations based on myths and misrepresentations. Therefore, it is necessary to train specialists capable of improving the field of historiography and deepen in the knowledge of the past from scientific assumptions. The process of political construction of the European Union faces, at present, a series of problems such as the mutual boundaries of sovereignty between its different members, harmonisation of entities with different cultural and historical traditions, even in conflict, and the necessity to look for a common ideological foundation that respects the identity of their members. The historical reflection and a better knowledge of the past, especially in the study of politic entities that faced similar problems, can contribute to a better understanding of current challenges. One of these is constituted, within the regional Southern Europe, by the Western Mediterranean territories, both Italian and Spanish, which were integrated in the Spanish Monarchy. That was imposed to its members like a project based on political loyalty to the Habsburg dynasty, identified with the defense of Catholicism, and regards to the territorial particularities that form the model of government of the Monarchy, which facilitated the consolidation and the permanence of identity traits -language, cultures, legal and political systems…- with the support by local leaders groups. With the disappearance of the Spanish Monarchy, the Spanish and Italian territories followed a different trajectory that culminated in the 19th century with their respective integration in the kingdoms of Spain and Italy. However, some of those identity traits have survived. The richness of this common history and its distinguishing traits require the training of specialists, who could develop direct research tasks based on the extensive archival materials, and reflection and synthesis from the historiographical sources.