Why did francis scott key write the star spsngled banner?

Hey there!

Contrary to what a lot of people believe, it wasn't written in revolutionary times, it was written a little afterward.

In fact, it was written in 1814, following the bombing of Fort McHenry. Bombs dropped, but when the American forces won, a torn flag was raised, which inspired the lines,

"the bombs bursting in air, gave proof through the night that the flag was still there"

Little did he know his song of unity would become the national anthem.

Hope this helps!