The valiant defense of the fort by 1,000 dedicated Americans inspired Francis Scott Key to write "The Star-Spangled Banner" during the Battle of Baltimore, September 13-14, 1814. Regardless of the rockets' red glare and the bombs bursting in air, the defenders of Fort McHenry stopped the British advance on Baltimore and helped to preserve the United States. Following the Battle of Baltimore during the War of 1812, the fort never again came under attack. However, it remained an active military post off and on for the next 100 years. It became an area administered by the National Park Service in 1933, two years after Key's poem became this country's National Anthem.