European union has been promoted since 1951 by means of a series of treaties - agreements with the force of law reached between member states.
The Treaty of Paris of 1951 established the European Coal and Steel Community (ECSC), which comprised Belgium, West Germany, France, Luxembourg, Italy and the Netherlands.
The Treaties of Rome of 1957 established the European Atomic Energy Community (EURATOM) and the European Economic Community (EEC), comprising the same six countries.
These three bodies were united by the Merger Treaty of 1967, under the name 'the European Economic Community'.
The EEC changed its name first to the European Community and latterly to the European Union, brought in new members and took on new powers and responsibilities under a series of additional treaties amending the previous agreements.
The most important of these are:
The Single European Act (in force 1987)
The Treaty on European Union or the Maastricht treaty (in force 1993)
The Treaty of Amsterdam (in force 1999)
The Treaty of Nice (in force 2003)
The Treaty of Lisbon (in force 2009)
The treaties established an independent system of law that takes precedence over national law, empowering EU institutions to make secondary legislation that member states are subject to.