The Community's initial aim was to bring about economic integration, including a common market and customs union, among its six founding members: Belgium, France, Italy, Luxembourg, the Netherlands and West Germany. It gained a common set of institutions along with the European Coal and Steel Community (ECSC) and the European Atomic Energy Community (EURATOM) as one of the European Communities under the 1965 Merger Treaty (Treaty of Brussels). In 1993, a complete single market was achieved, known as the internal market, which allowed for the free movement of goods, capital, services, and people within the EEC. In 1994, the internal market was formalised by the EEA agreement. This agreement also extended the internal market to include most of the member states of the European Free Trade Association, forming the European Economic Area covering 15 countries.
Upon the entry into force of the Maastricht Treaty in 1993, the EEC was renamed the European Community to reflect that it covered a wider range than economic policy. This was also when the three European Communities, including the EC, were collectively made to constitute the first of the three pillars of the European Union, which the treaty also founded. The EC existed in this form until it was abolished by the 2009 Treaty of Lisbon, which incorporated the EC's institutions into the EU's wider framework and provided that the EU would "replace and succeed the European Community".
The EEC was also known as the Common Market in the English-speaking countries and sometimes referred to as the European Community even before it was officially renamed as such in 1993.
In 1951, the Treaty of Paris was signed, creating the European Coal and Steel Community (ECSC). This was an international community based on supranationalism and international law, designed to help the economy of Europe and prevent future war by integrating its members.
In the aim of creating a federal Europe two further communities were proposed: a European Defence Community and a European Political Community. While the treaty for the latter was being drawn up by the Common Assembly, the ECSC parliamentary chamber, the proposed defense community was rejected by the French Parliament. ECSC President Jean Monnet, a leading figure behind the communities, resigned from the High Authority in protest and began work on alternative communities, based on economic integration rather than political integration. After the Messina Conference in 1955, Paul Henri Spaak was given the task to prepare a report on the idea of a customs union. The so-called Spaak Report of the Spaak Committee formed the cornerstone of the intergovernmental negotiations at Val Duchesse conference centre in 1956. Together with the Ohlin Report the Spaak Report would provide the basis for the Treaty of Rome.