Fort McHenry is most famous as the site of the battle where Francis Scott Key wrote The Star-Spangled Banner. It remained a fort through the Civil War, and a military property until after WWI, so over time it became quite different from how it looked in Key's time. It is now largely restored to that layout.

The 1812-configuration American flag that flies over the fort is a nylon replica of the original star-spangled banner that inspired the poem. The original was wool, 30 feet by 42 feet, so highly visible from a distance. See the Park Service website for PDFs of brochures of the fort's history (and a nice aerial photo of the star-shaped fort).

Most of the cannons on the site are from the Civil War era.

Where's the kaboom?

This is the mouth of the harbor that the fort defended.