In 1957 in the Italian city of Rome , the member countries signed another treaty and made the European Economic Community . Now it was a community for coal , steel and for trade . In 1957 , the six countries signed the Treaties of Rome , which extended the earlier cooperation within the European Coal and Steel Community ( ECSC ) and created the European Economic Community , ( EEC ) establishing a customs union and the European Atomic Energy Community ( Euratom ) for cooperation in developing nuclear energy .