<P> The EU 's predecessor , the European Economic Community , was founded with the Inner Six member states in 1958 , when the Treaty of Rome came into force . Since then , the EU 's membership has grown to twenty - eight , with the latest member state being Croatia , which joined in July 2013 . The most recent territorial enlargement of the EU was the incorporation of Mayotte in 2014 . The most notable territorial reductions of the EU , and its predecessors , were the exit of Algeria upon independence in 1962 and the exit of Greenland in 1985 . </P>
<P> The EU 's predecessor , the European Economic Community , was founded with the Inner Six member states in 1958 , when the Treaty of Rome came into force . Since then , the EU 's membership has grown to twenty - eight , with the latest member state being Croatia , which joined in July 2013 . The most recent territorial enlargement of the EU was the incorporation of Mayotte in 2014 . The most notable territorial reductions of the EU , and its predecessors , were the exit of Algeria upon independence in 1962 and the exit of Greenland in 1985 . </P>
which was the last country to join the eu
which was the last country to join the eu
Croatia
Croatia