Niihau (Hawaiian: ), anglicized as Niihau ( ), is the westernmost main and seventh largest inhabited island in Hawaii. It is southwest of Kauaʻi across the Kaulakahi Channel. Its area is . Several intermittent playa lakes provide wetland habitats for the Hawaiian coot, the Hawaiian 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 Niihau and the neighboring island and State Seabird Sanctuary of Lehua as Census Tract 410 of Kauai County, Hawaii. Its 2000 census population was 160, most of whom are native Hawaiians; Its 2010 census population was 170. At the 2020 census, the population had fallen to 84. Elizabeth Sinclair purchased Niihau in 1864 for from the Kingdom of Hawaii. The island's private ownership passed on to her descendants, the Robinsons. During World War II, the island was the site of the Niihau incident, in which, following the attack on Pearl Harbor, a Japanese navy fighter pilot crashed on the island and received help from the island's residents of Japanese descent. The island, known as "the Forbidden Isle", is off-limits to all outsiders except the Robinson family and their relatives, U.S. Navy personnel, government officials, and invited guests. From 1987 onward, a limited number of supervised activity tours and hunting safaris have opened to tourists. The island is currently managed by brothers Bruce and Keith Robinson. The people of Niihau are noted for their gemlike lei pūpū (shell lei) craftsmanship. They speak Hawaiian as a primary language. Geography Niihau is located about west of Kauai, and the tiny, uninhabited island of Lehua lies north of Niihau. Niihau's dimensions are 6.2 miles by 18.6 miles (10 km × 30 km). The maximum elevation (Paniau) is . The island is about 6 million years old, making it geologically older than the 5.8-million-year-old neighboring island of Kauai to the northeast. Niihau is the remnant of the southwestern slope of what was once a much larger volcano. The entire summit and other slopes collapsed into the ocean in a giant prehistoric landslide. Climate The island is relatively arid because it lies in the rain shadow of Kauai and lacks the elevation needed to catch significant amounts of trade wind rainfall. Niihau, therefore, depends on winter Kona storms for its rain, when more northerly weather systems intrude into the region. As such,