When the British attacked in 1814, guns of this type - but larger - were fired from the ramparts and the water batteries near the riverbank. They kept the British warships from entering Baltimore Harbor, but they could not shoot far enough to hit the vessels that were hurling bombs at the fort.
According to the American Commander's report, the British fired more than 1,500 bombs. These are the famous "bombs bursting in air" mentioned in our National Anthem. Displayed here are two which failed to explode. Fortunately, there were many duds and many misses, and the fort suffered little damage.
The gun tubes you see here are not known to have been at Fort McHenry during the bombardment. They are, however, authentic pieces from the War of 1812 period.