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.
Territories of the United States on stamps
The Panama Canal opening was commemorated on its 25th anniversary with a 3-cent stamp issued on August 15, 1939. The stamp shows a steamship passing through the Gaillard Cut, President Theodore Roosevelt on the left promoted the canal and General George W. Goethals on the right was chief engineer and first governor of the Panama Zone.