Panama Canal Zone (The Era of Relative Peace)

The Panama Canal Zone (Spanish: Zona del Canal de Panamá) 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 five miles (8.0 km) 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.

Joint U.S.-Panamanian control took place in the PCZ until December 31, 1999 when the Panama Canal was officially ceded to Panama.

World War III
The Panama Canal played an important role during World War III. Since the Canal was under the jurisdiction of the Panama Canal Zone, jointly controlled by the United State and the Republic of Panama, only allied warships, support ships, and merchant vessels were allowed to pass. The major U.S. bases in Panama like Howard Air Force Base and the Army base at Fort Clayton were on high alert in case of Soviet or Cuban activities within the Zone.