Why did they write the star spangled banner?

Answer 1

During the War of 1812, the lawyer and poet, Francis Key, was so moved by the sights of the war - the cannons the rockets, and so forth, that he wrote the poem about what he saw and named it, "'The Defence of Fort McHenry".

Someone shortly after that decided to add music for this poem, and called the resulting piece, "The Star-Spangled Banner", which was a very popular patriotic song for decades.

The music was from a popular British song written by John Stafford Smith for the Anacreontic Society, a men's club in London and was named, "The Anacreontic Song"

In 1939, Congress made "The Star-Spangled Banner" the official national anthem of the US, although the Marine Corps had been using it since 1899.

Answer 2

the lyrics come from "Defence of Fort McHenry" by Francis Scott Key after witnessing the bombing of Fort McHenry by the British Royal Navy.