Final answer:
The European Union was established with the ratification of the Maastricht Treaty in 1993, marking a significant step in the economic integration of Europe after World War II. Through expansion, the EU grew to twenty-seven member states by 2022, with a common currency, the euro, although not all members adopted it. The United Kingdom left the EU in a process completed in 2020.
Step-by-step explanation:
The European Union was created when the 12 nations of the European Community ratified the Maastricht Treaty of 1993, which introduced the common currency, the euro, and a commitment to common security and foreign policies. This historic agreement came after a series of efforts to integrate the economies of several European nations following the devastation of World War II. Initially beginning with a free trade association that evolved into the European Economic Community (EEC), it eventually led to the formation of the European Union as a full economic union.
Over time, the EU has expanded to include twenty-seven member states by 2022. A key focus of the EU has been to support the free movement of goods, services, money, and people across its member states. Despite the adoption of the euro by many of its members, some countries like the United Kingdom, Denmark, and Sweden have retained their own currencies. Additionally, in 2016, the United Kingdom voted to leave the EU, a process known as Brexit, which was completed in January 2020.