In the beginning, six countries – Belgium, Germany, France, Italy, Luxembourg and the Netherlands – founded the European Coal and Steel Community in 1951, followed by the European Economic Community and the European Atomic Energy Community in 1957.
Five successful enlargements have followed since then:
- In 1973, Denmark, Ireland and the United Kingdom joined the European Union.
- In 1981, Greece became a Member State.
- In 1986, Spain and Portugal became members.
- In 1995, Austria, Finland and Sweden joined the EU.
- In 2004, the EU underwent a historic enlargement to 10 countries of Central and Eastern Europe and the Mediterranean: Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovakia and Slovenia. It was a unique, historic enlargement which signified the re-unification of Europe after decades of division by an Iron Curtain.
The accession of Romania and Bulgaria on the 1 January 2007 completed the fifth enlargement of the EU that had started in May 2004.