United States territorial acquisitions
The Panama Canal Zone was an unorganized US territory located within the Republic of Panama. It was established under the Hay–Bunau-Varilla Treaty in 1903 and disestablished in 1979 under the Torrijos–Carter Treaties. Panama gained full control over the Panama Canal in 1999.
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.