Hawaii (Listeni/h??wa?.i?/ or /h??wa??i?/; Hawaiian: Hawai?i Hawaiian pronunciation: [h??v?i?i]) is the most recent of the 50 U.S. states (joined the Union on August 21, 1959), and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean.