The European Union was created through a series of treaties. These treaties were an attempt to heal the wounds caused by the devastation of World War II and create a spirit of harmony, trust, and cooperation among the countries of Europe for the benefit of its citizens and residents.
The three main treaties which formed the foundation for the European Union were the 1951 Treaty establishing the European Coal and Steel Community, known as the Paris Treaty, the 1957 Treaties of Rome, which established the European Atomic Energy Community and the European Economic Community, and the Merger (Brussels) Treaty, which combined those three communities into a single, unified entity.
The 1992 Treaty on European Union, or Maastricht Treaty, shortened 'the European Economic Community' to 'the European Community,' and facilitated cooperation between the governments of member nations on such issues as defense and criminal law.
The Treaties of Amsterdam and Nice were modifications of previous treaties. The Amsterdam Treaty of 1997 reconfigured and combined the EU and EC Treaties. The 2001 Treaty of Nice streamlined and merged with the EU and EC Treaties to form one version, modifying them to accommodate new nations joining the European Union and deal with global issues such as environmental and economic factors.
The Treaty of Lisbon in 2007 sought to create a greater cohesiveness within the European union as a whole, enhance the capabilities of the EU parliament, and provide ministers and members of parliament with greater accountability to its citizens.