The Northern Cook Islands is one of the two chains of atolls which make up the Cook Islands. Lying in a horizontal band between 9° and 13°30' south of the Equator, the chain consists of the atolls of Manihiki, Nassau, Penrhyn, Pukapuka, Rakahanga and Suwarrow, along with the submerged Tema Reef. Geography The chain forms a roughly inverted triangular shape, stretching from Penrhyn in the northeast to Pukapuka in the northwest and to Suwarrow in the south. The Northern Cook Islands are separated from the Southern Cook Islands by a wide stretch of the Pacific Ocean, with the nearest part of the Southern chain being Palmerston Island, due south of Suwarrow. With an area of just 21 sq. km. and a population of 1,041 (according to the 2016 census), the islands only account for some 6% of the Cooks' population and 9% of the land area. Almost all of this population is on the three islands of Pukapuka, Manihiki, and Penrhyn. The two chains are also geographically different: although both chains are formed from coral atolls which grew around volcanoes, the northern islands are far older, and the volcanic cones have sunk. As such, the northern chain is much lower lying than the southern chain. The two island chains are also parts of different marine ecoregions, with the Northern Cooks regarded as Central Polynesian and the Southern Cooks as Eastern Polynesian. Similarly, the land ecoregion in the Northern Cooks is Central Polynesian tropical moist forest whereas that of the southern chain is Cook Islands tropical moist forest. History The islands were settled by Polynesians for several centuries before the first European visitors, Spanish explorer Álvaro de Mendaña, navigator Pedro Fernandes de Queirós, and their crew reached and named the island of San Bernardo in 1595, now widely believed to have been Pukapuka. De Queirós returned to the region in 1606 in charge of his own vessel, making landfall at Rakahanga. The population of the chain was decimated by blackbirding during the 19th century, with the island of Tongareva (now more widely known as Penrhyn) being almost completely depopulated. At the end of the century, the chain became part of the Cook Islands Protectorate before the entire protectorate was annexed to New Zealand in 1900. From the 1850s until 1980, the United States laid claim to much of the northern chain under the Guano Islands Act. Despite this, the United States