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Fort McHenry, in Baltimore, Maryland, is a coastal star-shaped fort best known for its role in the War of 1812, when it successfully defended Baltimore Harbor from an attack by the British navy in Chesapeake Bay September 13–14, 1814. It was during the bombardment of the fort that Francis Scott Key was inspired to write "The Star-Spangled Banner," the poem that would eventually be set to the tune of "To Anacreon in Heaven" and become the national anthem of the United States.
Fort McHenry was built on the site of the former Fort Whetstone, which had defended Baltimore from 1776 to 1797.
During the American Civil War the area where Fort McHenry sits served as a military prison, confining both Confederate soldiers, as well as a large number of Maryland political figures who were suspected of being Confederate sympathizers.
The fort was also in use during World War I and II.
The fort was made a national park in 1925; on August 11, 1939, it was redesignated a "National Monument and Historic Shrine." -Wikipedia