American Samoa became a U.S. territory by deed of cession, starting in 1900. In 1878 the United States signed a treaty for the establishment of a naval station in Pago Pago Harbor. An 1899 agreement between colonial powers divided Samoa into spheres of influence: Germany gained control of the western islands, and the United States took the eastern islands. Formal cession by the local chiefs came later. By 1904 the eastern islands had all been ceded to the United States, although the U.S. Congress did not formally accept the deeds of cession until Feb. 20, 1929. Under the administration of the U.S. Navy (1900–51), American Samoa became a strategic naval base, but the Samoan leaders had little administrative power. In 1951 control of the territory was transferred to the U.S. Department of the Interior. The U.S. government appointed a governor who had full powers to administer the territory. The governor appointed political advisers and senior civil servants from the United States to help him.