to Penrhyn in 1854. Robert Louis Stevenson visited Penrhyn in May 1890. Slavery In the early 1860s, Penrhyn was almost completely depopulated by Peruvian blackbirding expeditions. In 1862 the ship Adelante took hundreds of Tongarevans aboard, ostensibly to transport them to a nearby island as agricultural workers. The Tongarevans went willingly: coconut blight had led to famine, while the local missionaries saw work overseas as a way of bring money to the atoll to pay for larger churches. Once on board, they were shackled in the hold and guarded day and night. 253 survived the voyage to reach Callao in Peru, where they were sold for between $100 and $200 each. Further slaving expeditions followed, and in total 472 Tongarevans were sold in Peru. Foreign claims Penrhyn was officially annexed for Great Britain by Captain Sir William Wiseman of HMS Caroline on 22 March 1888. The island was considered to have a strategic location on the route of a proposed Trans-Pacific telegraphic connection between Canada and Australia. The Cook Islands were a British protectorate 1888 to 1900, when annexed to New Zealand, until independence in 1965 when residents chose self-government in free association with New Zealand. From 1856 to 1980, the United States claimed sovereignty over the island under the Guano Islands Act. That claim had never been recognised by Britain, New Zealand or the Cook Islands and New Zealand sovereignty was recognised during World War II U.S. military operations involving the islands. On 11 June 1980, in connection with establishing the maritime boundary between the Cook Islands and American Samoa, the United States signed Cook Islands – United States Maritime Boundary Treaty acknowledging that Penrhyn was under Cook Islands sovereignty. World War II In early 1942 Japanese advances had placed the South Pacific air ferry route's initial path at some risk so that an alternate route was directed. In March Leif J. Sverdrup determined on a tour of potential island sites that Penrhyn was suitable and, though all land was owned by the local population and it was illegal to sell, use could be arranged and local labour could help build an airfield. U.S.Navy Seabees began work on a runway in July 1942 with aviation gasoline storage tanks added to the completed field. Two additional runways were added later. During the war, US Navy PBY Catalina and USAAF B-24 Liberator bombers were stationed on the island and with about