Image from Fort Mifflin
"The Fort That Saved America" got it's first taste of action in 1777 after Washington's defeat at Brandywine. He had to put distance between his Army and the redcoats and at the same time delay the British supply fleet at the mouth of the Delaware River. He sent 400 soldiers to Fort Mifflin, an unfinished British fortification, to hold off 2,000 redcoats and 200 ships.
They did both. Halting General Howe's troops for a month allowed Washington to get to Valley Forge and kept the fleet at sea. It's said that the cost in blood was over 275 men killed in the fort during that month.
The fort was later used as a prison for both Union and Confederate prisoners during the Civil War, and eventually closed in the 1960s. It's operated as a tourist attraction today. And there are plenty of spirits left in the old fort, enough to attract a crowd (or form one).
The most famous spook may be the Screaming Woman in the Officer Quarters.
She was thought to be Elizabeth Pratt by most paranormal story-tellers, based on a psychic's impressions. Pratt was, according to the lore, an officer's wife who had become estranged from her daughter when she ran off with an enlisted man. The daughter died of typhoid fever before they could reconcile, and the distraught mother hung herself.
But Tony Selletti in "Fort Mifflin: A Paranormal History" found that Elizabeth Pratt never lived in the area of the Officer's Quarters, but was housed with the officer's families on the grounds now occupied by the artillery shed, another area of ghostly activity. Elizabeth Bunker is now thought to be the woman; more on that as it comes out. (Thanks to Trish & Save Fort Mifflin for updating H&H; see their complete comments below.)
Whoever is yelling is doing a good job; her screams have been loud enough that the police have been called out on occasion to investigate.
The Man With No Face is thought to be Billy Howe, a prisoner that was hung for murder. He's spotted in the Casements, the prison cells of the fort, where he's usually seen wearing a hat and patching his clothes. His face is a black void. Often other soldiers and voices are also reported from the dungeon. One regular in the hoosegow is a soldier that is seen warming himself over a fire.
Jacob Sauer, the Blacksmith, is another popular spook. He's often seen in the smitty's shop, and the back doors he liked to keep open while working are still difficult to keep shut today. The Uniformed Guide, dressed in either a Civil War or Revolutionary war outfit (the versions differ) has taken tourists through the Powder Magazine. Except there wasn't any guide on duty, at least of the flesh and blood variety.
There's also the Lamplighter, allegedly the ghost of Joseph Adkins. Other ghosts include Edward, a poltergeist that likes to pull drawers open, and the Captain, who's been seen on the grounds apparently inspecting the troops. Once you're stationed at Fort Mifflin, you never get relieved.