The European Union was formally established when the Maastricht Treaty came into force on 1 November 1993, and in 1995 Austria, Sweden and Finland joined the newly established EU. In 2002, euro notes and coins replaced national currencies in 12 of the member states. Since then, the eurozone has increased to encompass sixteen countries, with Slovakia joining the eurozone on 1 January 2009. In 2004, the EU saw its biggest enlargement to date when Malta, Cyprus, Slovenia, Estonia, Latvia, Lithuania, Poland, the Czech Republic, Slovakia, and Hungary joined the Union.
After the end of the Second World War, moves towards European integration were seen by many as an escape from the extreme forms of nationalism which had devastated the continent. One such attempt to unite Europeans was the European Coal and Steel Community which, while having the modest aim of centralised control of the previously national coal and steel industries of its member states, was declared to be "a first step in the federation of Europe". The originators and supporters of the Community include Jean Monnet, Robert Schuman, Paul Henri Spaak and Alcide de Gasperi. The founding members of the Community were Belgium, France, Italy, Luxembourg, the Netherlands and West Germany.
In 1957, these six countries signed the Treaties of Rome which extended the earlier cooperation within the European Coal and Steel Community and created the European Economic Community, (EEC) establishing a customs union and the European Atomic Energy Community (Euratom) for cooperation in developing nuclear energy. In 1967 the Merger Treaty created a single set of institutions for the three communities, which were collectively referred to as the European Communities (EC), although commonly just as the European Community.
In 1973 the Communities enlarged to include Denmark, Ireland and the United Kingdom. Norway had negotiated to join at the same time but Norwegian voters rejected membership in a referendum and so Norway remained outside. In 1979 the first direct, democratic elections to the European Parliament were held.
Greece joined in 1981, and Spain and Portugal in 1986. In 1985 the Schengen Agreement led the way toward the creation of open borders without passport controls between most member states and some non-member states. In 1986 the European flag began to be used by the Community and the Single European Act was signed. The Iron Curtain's fall enabled eastward enlargement. (Berlin Wall)
In 1990, after the fall of the Iron Curtain, the former East Germany became part of the Community as part of a newly united Germany. With enlargement toward Eastern and Central Europe on the agenda, the Copenhagen criteria for candidate members to join the European Union were agreed.