The island of Maui (pron.: /ˈmaʊ.iː/; Hawaiian: [ˈmɐuwi]) is the second-largest of the Hawaiian Islands at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is part of the State of Hawaiʻi and is the largest of Maui County's four islands, bigger than Molokaʻi, Lānaʻi, and unpopulated Kahoʻolawe. In 2010, Maui had a population of 144,444, third-highest of the Hawaiian Islands, behind that of Oʻahu and Hawaiʻi Island. Kahului is the largest census-designated place (CDP) on the island with a population of 26,337 as of 2010 and is the commercial and financial hub of the island. Wailuku is the seat of Maui County and is the third-largest CDP as of 2010. Other significant places include Kīhei (including Wailea and Makena in the Kihei Town CDP, which is the second-most-populated CDP in Maui); Lahaina (including Kāʻanapali and Kapalua in the Lahaina Town CDP); Makawao; Pāʻia; Kula; Haʻikū; and Hāna.
The Haleakalā Observatory on the island of Maui, also known as the Haleakalā High Altitude Observatory Site, is the location of Hawaii's first astronomical research observatory. It is owned by the Institute for Astronomy of the University of Hawai'i, which operates some of the facilities on the site and leases portions to other organizations. Tenants include the Air Force Research Laboratory (AFRL) and the Las Cumbres Observatory Global Telescope Network (LCOGTN). At over 3,050 meters (10,010 ft) in altitude, the summit of Haleakalā is above one third of the Earth's atmosphere and has excellent astronomical seeing conditions.