Timeline

1951 – Europe of six: six ‘founding’ Member States (Belgium, France, Luxembourg, Italy, the Netherlands, and the Federal Republic of Germany) establish the ECSC (the European Coal and Steel Community).

1957 - The six ECSC Members States sign the Treaties of Rome. Establishment of the European Economic Community (EEC) and the European Atomic Energy Community (Euratom).

1973 - Europe of nine (first enlargement): accession of Denmark, the United Kingdom and Ireland.

1981 - Europe of ten (second enlargement): accession of Greece.

1986 - Europe of twelve (third enlargement): accession of Spain and Portugal.

1995 - Europe of fifteen (fourth enlargement): accession of Austria, Finland and Sweden.

20 June 2003 - The European Council reiterates its conclusions made in Copenhagen (December 2002) and Brussels (March 2003) and confirms “its determination to fully and effectively support the European perspective of the western Balkan countries, affirming that they will become an integral part of the European Union once they meet the established criteria”.

1 May 2004 - Europe of twenty-five (fifth enlargement): accession of Cyprus, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, Slovenia and the Czech Republic.

25 April 2005 - Treaty of Accession signed with Romania and Bulgaria.

3 October 2005 - Accession negotiations open with Turkey and Croatia.

15-16 December 2005 – European Council grants candidate country status to the Former Yugoslav Republic of Macedonia (FYRM).

1 January 2007 – Accession of Bulgaria and Romania (completion of fifth enlargement).

June 2010: The European summit has given the go-ahead for negotiations start on Iceland joining the European Union. Iceland is now the fourth candidate country, alongside Turkey, Croatia and the Former Yugoslav Republic of Macedonia.

December 2010 - the European Summit grants the status of candidate country to Montenegro

For more information:
The history of the European Union