Francis Scott Key wrote four verses for “The Star-Spangled Banner.”
Key originally wrote the words as a poem titled “Defence of Fort M’Henry” after watching the British bombardment of Fort McHenry near Baltimore on September 13–14, 1814. When dawn revealed the large American flag still flying above the fort, he began composing the poem aboard a British ship where he had been detained after helping negotiate the release of an American prisoner.
The poem was later set to the tune of “Anacreon in Heaven,” an English song associated with the Anacreontic Society. Although the complete anthem contains four verses, public performances almost always use only the first. That practice leads some people to assume the song itself has only one verse.
There is also an unofficial fifth stanza written by Oliver Wendell Holmes Sr. in 1861, during the Civil War. It is not part of Key’s original poem and is not counted in the standard answer. The song became the official U.S. national anthem on March 3, 1931.