The United States did not have a national anthem until 1931!
The poem “The Star-Spangled Banner” was actually written as over a hundred years earlier – all the way back in 1814 by Francis Scott Key! Over the years, the words were set to a British drinking song and the tune gradually gained patriotic popularity. In 1889, the song was adopted for official use by the Navy, and in 1916 it was given the presidential seal of approval. However, the song was not officially named our national anthem until March 3, 1931, when President Herbert Hoover signed a congressional resolution!
(Sources: 1, 2)