Which of the treaty was signed amongst the European nations for entering into the monetary union?

The Maastricht Treaty was approved by heads of government of the states making up the European Community (EC) in December 1991. The treaty required voters in each country to approve the European Union, which proved to be a hotly debated topic in many areas. The agreement took ended with the creation of the European Union and has since been amended by other treaties. The Maastricht Treaty was signed on February 7, 1992, by the leaders of 12 member nations (Belgium, Italy, Luxembourg, France, Netherlands, West Germany, Denmark, Ireland, United Kingdom, Greece, Portugal and Spain). The treaty entered into force November 1, 1993.