When was the national athem of united states created?

Francis Scott Key wrote the poem "Defence of Fort M'Henry" in September 1814, after witnessing the massive bombardment of Fort McHenry by British ships of the Royal Navy in Chesapeake Bay during the Battle of Baltimore in the War of 1812. Inspired by the large U.S. flag, measuring 30 by 42 feet (9.1 by 12.8 m), known as the Star-Spangled Banner, flying triumphantly above the fort during the U.S. victory, he wrote the poem which was later set to the tune of the British song "To Anacreon in Heaven" by John Stafford Smith. The song was sung by American soldiers during the Mexican–American War.

During the American Civil War, Union troops often sang "The Star-Spangled Banner" while Confederate troops sang "Dixie" as both sides went into battle.[citation needed] Despite its growing popularity, "The Star-Spangled Banner" was not designated as the national anthem of the United States until President Woodrow Wilson issued a proclamation to that effect on December 31, 1915, after it was performed at the 1915 Panama–Pacific International Exposition.[1] It was made the official anthem by a congressional resolution on March 3, 1931, and signed into law by President Herbert Hoover.[2][3]