The European Union has its roots in the 1951 agreement by France, Germany and four other countries to pool coal and steel supplies, with the aim of ending "age-old rivalries".
The European Coal and Steel Community came into existence in July 1952. The Treaty of Rome creating a broader "common market" was signed five years later.
The first enlargement took place in 1973. The sixth enlargement occurred on 1 January 2007.