History of the Panama Canal
During World War II, the canal proved a vital part of the U.S. military strategy, allowing ships to transfer easily between the Atlantic and Pacific. Politically, the Canal remained a territory of the United States until 1977, when the Torrijos–Carter Treaties began the process of transferring territorial control of the Panama Canal Zone to Panama, a process completed on 31 December 1999.
United States Southern Command
The Marines protected the Panamanian civilian uprising led by former Panama Canal Company general manager Philippe-Jean Bunau-Varilla guaranteeing his creation of the Panamanian state. Following the signing of the Hay–Bunau-Varilla Treaty granting control of the Panama Canal Zone to the United States, the Marines remained to provide security during the early construction days of the Panama Canal.