Final answer:
Francis Scott Key visited Baltimore during the War of 1812 to negotiate the release of an American prisoner. He witnessed the British bombardment of Fort McHenry and the survival of the American flag after the attack, which inspired him to write 'In Defense of Fort McHenry', later known as 'The Star-Spangled Banner'.
Step-by-step explanation:
Francis Scott Key went to Baltimore during the War of 1812, specifically after the event of the British bombardment of Fort McHenry in 1814. Key was there to negotiate the release of an American prisoner held by the British. He found himself witnessing the bombardment of the Fort during these negotiations, which is where he saw the American flag waving proudly despite the attack, which inspired him to pen his famous poem 'In Defense of Fort McHenry.'
This poem was not just an observation, but a declaration of the American triumph and resilience, against all odds. Later, this poem was adapted to a British song called 'The Anacreontic Song,' which eventually took the form of the United States' national anthem, known as 'The Star-Spangled Banner' today. Hence, what Key 'brought' with him to Baltimore was an unfailing American spirit, which found its expression through this famous poem.
Learn more about Francis Scott Key