What inspired Francis Scott Key to write "The Star Spangled Banner"?

The poem used to be called "The Defence of Fort McHenry." It was written after he watched the Maryland fort get bombed by the British during the War in 1812.

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On this day in 1814, Francis Scott Key pens a poem which is later set to music and in 1931 becomes America's national anthem, "The Star-Spangled Banner." The poem, originally titled "The Defence of Fort McHenry," was written after Key witnessed the Maryland fort being bombarded by the British during the War of 1812.