Which song became the official national anthem of the United States when Congress adopted it in 1931?

The Star-Spangled Banner became the official national anthem of the United States when Congress adopted it in 1931.

The song's lyrics came from a poem by Francis Scott Key, who wrote them after watching the bombardment of Fort McHenry during the Battle of Baltimore on September 14, 1814. Key saw the large American flag still flying over the fort after the night attack and shaped his poem around that sight.

The words were later set to the melody of a British song associated with the Anacreontic Society. The tune was already popular in the United States, helping the patriotic song spread during the 19th century. The United States Navy recognized it for official use in 1889, and President Woodrow Wilson ordered it played at military and other appropriate occasions in 1916.

Congress passed the national-anthem resolution on March 3, 1931, and President Herbert Hoover signed it the next day. The song has four official stanzas, but public performances usually use only the first.