On February 7, 1992, the Maastricht Treaty was signed creating the European Union. The Union was a step towards greater integration from the previous Common Market.
In December 1991 negotiations began between the nations of the Common Market to extend the scope of their relationship beyond just economic trade. The new treaty extended that cooperation to a common foreign and defense policy while also creating cooperation in the Field of Justice and Home Affairs. The treaty further integrated the economic cooperation between the countries which led to the creation of a common currency the Euro.
The treaty was then submitted for ratification by the participating. Three counties were forced to hold referendums: Denmark, France and Ireland. In all three cases the treaty was eventually ratified by the narrowest margins.