The European Council is today an important and powerful institution in the EU. Starting as just informal meetings among the leaders of the European community in the 1960's, it has now developed and has become one of the seven institutions in the European Union. The study uses Historical Institutionalism as theory and process-tracing as method. Historical Institutionalism is providing the paper with the analysis tools. With critical juncture, positive feedbacks, path-dependency and sequencing as analysis tools the paper is explaining and analyzing the European Council from an historical institutionalistic perspective and also is identifying actors that are either promoting the progress of the European Council or are opponents of the progress of the European Council. The study shows that the critical juncture took place at the summit in Paris 1974 and therefore the institution was led into path dependency. The result of the critical juncture and the path dependency is that the institution is lacking options of changing itself. Instead the critical juncture is making the institution predictable in regard to which direction it's going to take due to the positive feedbacks and sequencing and therefore it is just going deeper in the path-dependency and making it harder to change direction the further down the same path the institution is going. Looking at the history, the study shows that the leaders of Germany and France has been important actors for institutional development for the European Council, but that the United Kingdom and Denmark often in the history has been negatively of institutional change, no matther who's prime minister at the time.