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.
United States involvement in regime change
In 1903, the U.S. aided the secession of Panama from the Republic of Colombia. The secession was engineered by a Panamanian faction backed by the Panama Canal Company, a French–US corporation whose aim was the construction of a waterway across the Isthmus of Panama thus connecting the Atlantic and Pacific Oceans. In 1903, the U.S. signed the Hay-Herrán Treaty with Colombia, granting the United States use of the Isthmus of Panama in exchange for financial compensation. amidst the Thousand Days' War. The Panama Canal was already under construction, and the Panama Canal Zone was carved out and placed under United States sovereignty. The US did not transfer the zone back to Panama until 2000.