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.
History of Panama (1821–1903)
The Republic of Panama became a de facto protectorate of the larger country through two provisions whereby the United States guaranteed the independence of Panama and received in return the right to intervene in Panama's domestic affairs. For the rights it obtained, the United States was to pay the sum of US$10 million and an annuity, beginning 9 years after ratification, of US$250,000 in gold coin. The United States also purchased the rights and properties of the French canal company for US $40 million.