He is known for a poem he wrote in September 1814 during the War of 1812. The British Army had captured and burned Washington and the fleet was sailing to Baltimore. The British had captured a well know physician, Dr. William Beanes. Francis Scott Key went with Col. John Skinner to meet with British officers aboard the HMS Tonnant to negotiate the release of Beanes. They gained his released, but were prevented from returning to Baltimore until after the British attack on Fort McHenry. The next morning, after 25 hours of shelling, Key saw the large stars and stripes flag still flying and drafted a poem on "The Defence of Ft McHenry". After returning to Baltimore, he finished the poem and it was printed and circulated in Baltimore. It then appeared in newspapers and was sung to the tune "Anacreon in Heaven". The song became popular as "The Star spangled Banner" though it was not until 1931 that Congress officially declared it to be the National Anthem. The flag from Ft. McHenry is now in the Smithsonian.
Francis Scott Key's birthplace "Terra Rubra" is near Keymar, Maryland. The present house is not the original one built in the 1770's for his father. After Key died, the house was sold and deteriorated. It was demolished after further damage by a storm and the present brick house was built. Terra Rubra was listed in the Maryland Historic Trust in 1978.