national anthem of the United States of America, in which the words of an 1814 poem by Francis Scott Key (1779-1843), The Defence of Fort McHenry, are set to the tune of a popular British drinking song of the era. It was in regular use by the Navy and President in the late 19th and early 20th centuries, but was not formally adopted until 1931.
Today, only the first stanza of Key's poem is generally sung, with the fourth added occasionally. However, it is the fourth stanza which provides the phrase 'In God we trust', the US motto since 1956. The opening stanza describes rockets bursting over Fort McHenry, Baltimore, in defence of US freedom against British attack. The 'star spangled banner' is the American flag, decorated with the stars and stripes to represent the first and existing states of the union.