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Due to geographical proximity of the Central American countries to the U.S. which has powerful military, economic, and political influences, there were several movements and proposals by the United States during the 19th and 20th centuries to annex some or all of the Central American republics (Costa Rica, El Salvador, Guatemala, Honduras with the formerly British-ruled Bay Islands, Nicaragua, Panama which had the U.S.-ruled Canal Zone territory from 1903 to 1979, and formerly British Honduras or Belize since 1981). However, the U.S. never acted on these proposals from some U.S. politicians; some of which were never delivered or considered seriously. In 2001, El Salvador adopted the U.S. dollar as its currency, while Panama has used it for decades due to its ties to the Canal Zone.

When did the British have the US-ruled Canal Zone Territory?
unanswerable