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.
Panama–United States relations
The 1977 Panama Canal Treaties entered into force on October 1, 1979. They replaced the 1903 Hay–Bunau-Varilla Treaty between the United States and Panama (modified in 1936 and 1955), and all other U.S.-Panama agreements concerning the Panama Canal, which were in force on that date. The treaties comprise a basic treaty governing the operation and defense of the Canal from October 1, 1979 to December 31, 1999 (Panama Canal Treaty) and a treaty guaranteeing the permanent neutrality of the Canal (Neutrality Treaty).