From www.gutenberg.org/etext/21566

"The Star-Spangled Banner" is the national anthem of the United States. The lyrics come from the "Defence of Fort M'Henry", a poem written on September 14, 1814, by 35-year-old lawyer and amateur poet Francis Scott Key after witnessing the bombardment of Fort McHenry by British ships of the Royal Navy in Baltimore Harbor during the Battle of Baltimore in the War of 1812. Key was inspired by the large U.S. flag, with 15 stars and 15 stripes, known as the Star-Spangled Banner, flying triumphantly above the fort during the U.S. victory.
The above text from the Wikipedia article "The Star-Spangled Banner" text is available under CC BY-SA 3.0.