Between 2010 and 2013 the European Science Foundation project "Cuius Regio" undertook a study of the reasons for cohesion of some European regions, including the analysis of the ways for cohesion of two peripherical Iberian entities: Portugal and Catalonia. A scientific meeting held in Lleida in 2012 facilitated the collection of contributions from outstanding researchers in order to analyse how specific identities in the periphery of the Iberian Peninsula were created in the Middle Ages and how they evolved until the 19th century. History, Literature and Language are being discussed in this book in order to understand the reasons for creating specific territorial identities and also to compare their different evolutions, that have resulted in different political realities in our current times.