Panama Canal Zone
The Panama Canal Zone () was an unincorporated territory of the United States from 1903 to 1979, centered on the Panama Canal and surrounded by the Republic of Panama. The zone consisted of the canal and an area generally extending on each side of the centerline, excluding Panama City and Colón, which otherwise would have been partly within the limits of the Zone. Its border spanned three of Panama's provinces. When reservoirs were created to assure a steady supply of water for the locks, those lakes were included within the Zone.
Mexico–Panama relations
During the 1970s, Mexico became a vocal supporter for dialogue between Panama and the United States for eventual Panamanian control of the Panama Canal. In 1977, Panama and the United States signed the Torrijos–Carter Treaties giving Panama eventual control of the canal in December 1999. During the 1980s, foreign ministers of Colombia, Mexico, Panama and Venezuela created the Contadora Group in order to diplomatically try to resolve the crisis facing many Central American nations at the time.