Hawaii became the 50th U.S. state on August 21, 1959, completing the current state union.
Congress passed the Hawaii Admission Act in 1959, and President Dwight D. Eisenhower signed it on March 18. Hawaii then held a statehood referendum on June 27, in which voters approved statehood overwhelmingly. The formal admission date came later that summer.
Hawaii’s admission followed Alaska’s, which became the 49th state on January 3, 1959. The two admissions ended a long period in which the United States had 48 states. Hawaii is the only U.S. state made up entirely of islands and the only state located outside North America geographically.
A common mix-up is confusing the admission date with the referendum or the signing of the admission law. Those were separate steps. August 21 is celebrated as Statehood Day in Hawaii and marks its formal entry into the Union.