In 1957, the Treaty of Rome was signed by six West European states to create the European Economic Community (EEC). Designed to foster a common internal market for a limited amount of industrial goods and to define a customs union within the Six, it did not at the time particularly stand out among contemporary international organizations. However, by 1992, within the space of a single generation, this initially limited trade zone had been dramatically expanded into the world's largest trade bloc and had pooled substantial sovereignty among its member states on a range of core state responsibilities. Most remarkably, this transformation resulted from a thoroughly novel political experiment that combined traditional interstate cooperation among its growing membership with an unprecedented transfer of sovereignty to centralized institutions. Though still lacking the traditional institutions and legitimacy of a fully-fledged state, in many policy areas, the European Union (EU) that emerged in 1992 was nonetheless collectively a global force. My dissertation argues that the organization's unprecedented transfer of national sovereignty challenged the very definition of the modern European state and its function. In structure and ambition, it represented far more than just a regional trade bloc among independent states: it became a unique political entity that effectively remodelled the fundamental blueprint of the conventional European state structure familiar to scholars for generations. How did such a dramatic transformation happen so quickly? I argue that three forces in particular were at play: the external pressures of globalization, the search for a new Western European and German identity within the Cold War world and the often unintended consequences of the interaction between member state governments and the Community's supranational institutions. In particular, I examine the history of the EEC's monetary union, common foreign policy, common social policy and the single market to explain the impact of the above forces of change on the EEC's rapid transformation.