The roots of the European Commission lie in the High Authority of the ECSC, which consisted of nine members, was headquartered in Luxembourg and started its work in 1952. Although Jean Monnet, the President of this first Commission, hoped this supranational institution would be independent and powerful, the Member States have decided to create the Council of Ministers, intergovernmental in nature, to counter-balance its powers (McCormick, 2011 B, p.168). I hope you remember that from the discussion on the intergovernmental character of the Council of Ministers.
In 1967, the ECSC High Authority was merged with the commissions for the EEC and the Euratom into a Commission of the European Communities. The European Commission emerged. With the growing membership of the Community in the 1970s and 1980s, the number of Commissioners expanded with two more added for each large Member State joining and one added for a small new member. Under the Nice Treaty (2003), the size of the Commission was changed and since then until the present day each Member State of the EU has only one Commissioner. Since Croatia joined the EU in 2013, the European Commission consists of 28 Commissioners..
The Commission saw its powers declining over the years. First, in the 1960s after the so-called ‘empty chair crisis’. Then in 1974, with the creation of the European Council, and finally in 1979, when direct elections of the European Parliament were introduced. Only in the late 1980s and early 1990s was the Commission’s position stronger, as it was moving forward with the single market project under Jacques Delors. Today, its powers have been declining again but its visibility has been increasing (McCormick, 2011 B, p.168).
Do not worry, here is a recap of what the empty chair crisis was, if you do not remember.