Large hill directly to the south of the Inner Harbor in Baltimore, and the neighborhood directly to the south of the hill.
So named because it was here that the city government threw a party to celebrate Maryland's ratification of the U.S. Constitution.
The hill commands an excellent view of a wide swath of Baltimore, roughly from Camden Yards to Canton. Due to this, it was occupied during the War Between The States by Union artillery, which allowed the Federals to keep secession-crazed Baltimore under martial law; they could have responded to any kind of uprising with a punishing barrage of the business district, city hall, and the harbor.
Now, since no node is complete without some 80s music trivia, I should mention that the Talking Heads song And She Was is about a friend of David Byrne's who dropped acid on Federal Hill.
Thanks to czeano for contributions to this writeup.