During a press conference earlier this month, German chancellor Angela Merkel had something of a disagreement with President Donald Trump.

After Trump claimed that German trade negotiators, in securing trade deals with the United States, “have done a far better job than the negotiators for the United States,” Merkel was forced to clarify: Germany does not have its own trade negotiators. Nor does the country agree its own trade accords. Germany’s trade agreements are arranged through the European Union (EU). This is true for all twenty-eight member states. And it has been for a long time.

The treaty establishing the European Economic Community (EEC), the precursor to the European Union, was signed sixty years ago this month, on March 25, 1957. Commonly known as the Treaty of Rome, the accord set up a customs union and common market between Belgium, France, Italy, Luxembourg, the Netherlands, and West Germany. It also granted the EEC the power to handle external trade relations for its members.