Technically no country joined the EU before 1972, as it did not officially come into existence until 1993. However it existed in a different form prior to that. In 1957 France, West Germany, Italy, Belgium, the Netherlands and Luxembourg formed the European Economic Community, which eventually became the European Union. The next countries to join didn't join until 1973, so the listed countries are the countries that you are probably looking for.
Actually, it was in 2004. The following countries joined the EU.CyprusCzech RepublicHungaryEstoniaLatviaLithuaniaMaltaPolandSloveniaSlovakia
No countries joined the EU in 2010. Before 2010, Romania and Bulgaria were the newest, joining in 2007.
Hungary joined the EU in 2004, but has not yet joined the Euro currency.
Until 2002 the Belgian Franc
No countries joined the EU in 2008. 10 countries joined in 2004. See the related question below.
Bulgaria has not yet joined the Euro zone, it joined the EU in January 2007.
Sweden joined the EU in the year of 1995.
Finland joined the EU in the 1995.
No new country joined the EU in 1999.
On the 1st May 2004 Hungary joined the EU (European Union)
Malta joined the European Union on the 1st of May in 2004.
The United Kingdom joined the Common Market in 1973.