When and why did Hawaii become a state? Hawaii—a U.S. territory since 1898—became the 50th state in August, 1959, following a referendum in Hawaii in which more than 93% of the voters approved the proposition that the territory should be admitted as a state. There were many Hawaiian petitions for statehood during the first half of the 20th century. These were denied or ignored. Some in the U.S. had been convinced, even at the time of Hawaii’s annexation, that Hawaii had no natural connection to the rest of the states.