This volume explains the national and regional border modifications that took place in Europe from 1870 to 2020. It provides insights that allow us to understand boundary changes for several different levels of territorial organization. The text describes the state formation process related to the regional-administrative structures in each European country, and offers insight into the degree of centralization historically by describing the extent of legislative autonomy at different administrative levels and the competences reserved for each of them. to the book sheds light on the complex regional organization of Europe and the difficulties its reform has faced. The main audience will be academics and PhD/Masters students working in a variety of geography fields, and the maps included in each chapter will also be of interest to a broader audience including undergraduate and secondary-school students wishing to better understand the political history of Europe.