The Star-Spangled Banner

On September 14, 1814, Francis Scott Key penned the poem "Defence of Fort M'Henry" which later became known as "The Star-Spangled Banner". From the article:

"“The Star-Spangled Banner” is the national anthem of the United States. By the time the song officially became the country’s anthem in 1931, it had been one of America’s most popular patriotic tunes for more than a century. The anthem’s history began the morning of September 14, 1814, when an attorney and amateur poet named Francis Scott Key watched U.S. soldiers—who were under bombardment from British naval forces during the War of 1812—raise a large American flag over Fort McHenry in Baltimore, Maryland."