The North American Union (NAU) is a theoretical economic and political continental union of Canada, Mexico and the United States, the three largest and most populous countries in North America. The concept is loosely based on the European Union, occasionally including a common currency called the amero or the North American Dollar. A union of the North American continent, sometimes extending to Central and South America, has been the subject of academic concepts for over a century, as well as becoming a common trope in science fiction. One reason for the difficulty in realizing the concept is that individual developments in each region have failed to prioritize a larger union. Some form of union has been discussed or proposed in academic, business, and political circles for decades. However, government officials from all three nations say there are no plans to create a North American Union and that no agreement to do so has been proposed, much less signed. The formation of a North American Union has been the subject of various conspiracy theories. History Since at least the mid-19th century, numerous concepts for a union among Canada, Mexico and the United States, some including the Caribbean, the Central American and the South American countries, have been proposed, such as the North American Technate. Following the Maastricht Treaty and the North American Free Trade Agreement (NAFTA) going into effect in the early to mid-1990s, there was speculation about the formation of a North American Union, similar to the European Union created by Maastricht, being a possible future step for the region. Several proposals for continental integration of North America advocated the creation of a union styled after the European Union, though many academic and business groups advocated less dramatic changes involving the formation of a customs union or common market. While serving as a policy adviser to the presidential campaign of Vicente Fox during the 2000 general election in Mexico, Jorge Castañeda, influenced by American academic Robert Pastor's ideas on deepening integration of NAFTA, encouraged Fox to include policies on integration as part of his campaign. Before and after the election Fox made appearances on several U.S. news programs advocating greater integration including a plan to open up the U.S.-Mexico border within ten years. Some in the United States saw this proposal for open borders as a call for or inevitable step towards a "North American Union" and received it with