Students of European integration have come to argue that the European Union (EU) is a system of ‘compounded’ or ‘mixed’ representation characterized by the presence of different forms and styles of political representation which reflect the ideas and strategic interests of various groups of actors and institutions. The EU's system of representation did not come about by fiat. Among the founders of Europe's first supranational community, the European Coal and Steel Community (ECSC), ideas about appropriate institutional mechanisms to represent different sets of interests were hotly contested. This article traces the origins of the EU's system of representation by sketching the answers given by the ‘founding fathers’ of the ECSC to questions about which interests should be represented in the nascent ECSC and how the representation of these interests should be institutionally manifested. It also takes issue with the current debate about the ‘democratic challenge’ faced by the EU's system of representation and offers a set of research questions which could help to advance the research agenda.