How many stars and stripes appeared on the U.S. flag that inspired “The Star-Spangled Banner”?

The flag that inspired “The Star-Spangled Banner” had 15 stars and 15 stripes.

Francis Scott Key saw the flag flying over Fort McHenry after the British bombardment during the Battle of Baltimore on September 14, 1814. Its design reflected the United States' admission of Vermont and Kentucky, which brought the number of states to 15.

The 15-star, 15-stripe design was authorized by the Flag Act of 1794. Congress later concluded that adding a stripe for every new state would make the flag unwieldy, so the flag returned to 13 stripes in 1818 while continuing to add stars for new states. The Smithsonian's preserved flag is much larger than an ordinary modern flag and shows evidence of repairs and cutting over time.

The national anthem's title refers to this specific wartime flag. It is often confused with the modern U.S. flag, which has 13 stripes and a star for each current state.