Austria, Finland, and Sweden join the European Union
With the fourth enlargement, the 15 members covered almost all of Western Europe. The accession of these three countries forced the reorganization of the European Free Trade Assocation (EFTA) and broadened the diversity of population.
European Central Bank is inaugurated in Frankfurt, Germany
The euro is adopted as the single currency
The introduction of the euro in 1999 was a major step in European integration: more than 333 million EU citizens now use it as their currency.
National currencies are replaced by euro notes and coins
Ten new Member States join the EU
Czech Republic, Cyprus, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, and Slovenia.
EU welcomes Switzerland to the Schengen area
Treaty of Lisbon enters into force
Estonia joins the Euro area
Croatia joins the EU
Latvia adopts the euro as its currency
Lithuania adopts the euro
United Kingdom holds a Membership Referendum and votes to secede from the EU