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.
History of Panama
The Panama Canal was built by the U.S. Army Corps of Engineers between 1904 and 1914; the existing 83-kilometer (50-mi.) lock canal is considered one of the world's great engineering triumphs. On January 5, 1909 the government of Rafael Reyes in Colombia signed and presented to its Congress a treaty that would officially recognize the loss of its former province, but the treaty was not ratified, due to popular and legislative opposition. Negotiations continued intermittently until a new treaty was signed on December 21, 1921 which formally accepted the independence of Panama.