Fort McHenry guarded the entrance to the harbor of Baltimore. After the British had burned America's capital city, they set their sights on Baltimore, a wealthy city ripe for looting and the home port of many of the American privateers that had ravaged British shipping.
On September 13, 1814, the British fleet attacked. The city and the fort were under blackout orders to make it harder for the gunners to aim. Only the British rockets and bombs illuminated the night sky. They revealed the 30 by 42-foot flag sewn by Mary Pickersgill, her daughter Caroline, and three other children: Eliza Young, Margaret Young, and Grace Wisher.
In the 1870s, George Henry Preble, an American naval officer, wrote a series of histories of the United States flag. As a part of his work, he took the earliest known photograph of then 59-year old Star-Spangled Banner.
-via American Digest