April 1951: Belgium, France, Germany, Italy, Luxembourg and the Netherlands sign the Treaty of Paris, establishing the European Coal and Steel Community (ECSC), creating the foundation for a common market in the coal and steel industry.
March 1957: ECSC members sign the Treaty of Rome establishing the European Economic Community (EEC), with the aim of gradually forming a common agricultural and industrial market.
July 1967: The ECSC, EEC and the European Atomic Community (Euratom) merge under a single organization, the European Community (EC). A customs union is established the following year.
September 1972: Referendum on Norway joining the EC fails.
January 1973: Britain, Denmark and Ireland become members of the EC.
March 1979: European Monetary System enters into force, a first step towards a single European currency.
January 1981: Greece becomes 10th member of the EC.
January 1986: Spain and Portugal become EC members.
April 1987: Turkey formally applies to join the EC.
June 1993: Four years after the fall of the Berlin Wall, Copenhagen summit establishes political and economic criteria for Eastern and Central European candidates to join the EC.
November 1993: The Treaty of Maastricht transforming the EC into the European Union (EU) comes into force.
November 1994: Norway again rejects referendum on joining EU.
January 1995: Austria, Finland and Sweden join the EU, which now includes 15 member states with a population of about 370 million, covering about 3.2 million square kilometres (1.2 million square miles).
March 1995: Schengen Agreement removing passport checks on EU borders comes into force. Britain and Ireland opt out.
December 1997: Luxembourg summit decides to open accession talks with Cyprus, the Czech Republic, Estonia, Hungary, Poland and Slovenia. Agreement to establish European Conference, to include countries, notably Turkey, in the EU enlargement project.
January 1999: Launch of the single European currency, the euro.
December 1999: Helsinki summit agrees to open membership negotiations with Bulgaria, Latvia, Lithuania, Malta, Romania and Slovakia. Turkey recognized as a candidate state.
December 2000: Nice summit sets out timeframe and reforms necessary for enlargement.
January 2002: Euro becomes legal tender in 12 EU countries.
November 2002: EU foreign ministers fix May 1, 2004 for the accession of the 10 candidates, pending formal invitations from leaders at the December summit in Copenhagen.