<Tr> <Th> Population </Th> <Td> 170 (2010) </Td> </Tr> <Tr> <Th> Pop . density </Th> <Td> 1.9 / sq mi (0.73 / km) </Td> </Tr> <P> Ni ʻihau (/ ˈniːhaʊ /; Hawaiian: (ˈniʔiˈhɐw)) is the westernmost and seventh largest inhabited island in Hawai ʻi . It is 17.5 miles (28.2 km) southwest of Kaua ʻi across the Kaulakahi Channel . Its area is 69.5 square miles (180 km). Several intermittent playa lakes provide wetland habitats for the Hawaiian coot, the black - winged stilt, and the Hawaiian duck . The island is designated as critical habitat for Brighamia insignis, an endemic and endangered species of Hawaiian lobelioid . The United States Census Bureau defines Ni ʻihau and the neighboring island and State Seabird Sanctuary of Lehua as Census Tract 410 of Kauai County, Hawaii . Its 2000 census population was 160; Its 2010 census population was 170 . </P> <P> Elizabeth Sinclair purchased Ni ʻihau in 1864 for $10,000 from the Kingdom of Hawaii and private ownership passed on to her descendants, the Robinson family . During World War II, the island was the site of the Ni ʻihau Incident: A Japanese navy fighter pilot crashed on the island and terrorized its residents for a week after the attack on Pearl Harbor . The people of Ni ʻihau are known for their gemlike lei pūpū (shell lei) craftsmanship, and speak Hawaiian as a primary language . The island is generally off - limits to all but relatives of the island's owners, U.S. Navy personnel, the Robinson family, government officials and invited guests, giving it the nickname "The Forbidden Isle ." Beginning in 1987, a limited number of supervised activity tours and hunting safaris have opened to tourists . The island is currently managed by brothers Bruce Robinson and Keith Robinson . </P>

Is niihau a part of the united states