This chapter surveys the historical evolution of the European Union in four sections. Section 1 starts with the humble origins of the Union: the European Coal and Steel Community (ECSC), which was set up by the 1951 Treaty of Paris. While limited in its scope, the ECSC introduced a supranational idea that was to become the trademark of the European Economic Community (EEC). Section 2 focuses the EEC, while Section 3 investigates the development of the (old) European Union founded through the Treaty of Maastricht. Finally, Section 4 reviews the reform efforts leading to the Lisbon Treaty, and analyses the structure of the—substantively—new European Union as it exists today. Concentrating on the constitutional evolution of the European Union, the chapter does not present its geographic development.