A week ago, very late on Sunday night, fire broke out in the attic of the officers' quarters, a two-story, early 19th-century brick building.
The Philadelphia Fire Department responded quickly, and fire damage was contained to the attic. Water and smoke damage, however, spread throughout.
There were no injuries, and the fire is still under investigation.
Elizabeth Beatty, executive director of Fort Mifflin, a National Historic Landmark widely known for its role in the Revolutionary War, but also actively used in the War of 1812, the Civil War, and on up until the 1950s, when it was decommissioned, said there was no significant damage to original artifacts or documents.
"The damage to the building is from fighting the fire - the holes in the roof, the blown-out windows, the water damage," she said. The smell of wet, burned wood lay heavily across the fort.
"That's what we're addressing today - all that wet insulation. It is a heavy, dirty job."
That said, volunteers from all over the area turned out to lend a hand. And, Beatty said, despite the fire, the fort is proceeding with all of its scheduled events, including the U.S. Colored Troops Civil War weekend on April 4 and 5, and the President's Plate: Dining with Thomas Jefferson, April 19.
There was a lot to do, she said, between now and then. But help is there.
Christine Schum, 46, from North Cape May, interrupted her work sweeping the barracks to say her family had been volunteering for fort cleanup days for a decade.
"They needed us," she said. "The fort is very dear to us."
Schum is an active member of the Kingdom of Lucerne, a living-history group focused on the Middle Ages and the Renaissance. Every year, the kingdom holds its School of the Musketeer at the fort, filling the old brick battlements with tunic-bedecked archers and lace-capped bakers.
Cathy Lieby, 43, from Bainbridge in Lancaster County, is also into living history, although she is more inclined to the military engagements of the 16th and 17th centuries as a member of the Twisted Knot Company of Pike & Shot.
Fort Mifflin is not just historic to her, she said, it is real in a way that goes beyond the buffed-up historic sites of Center City.
"In Center City, you can read about it, look at it, but here, you can do it," she said. "Wow! This is how it was."
Jamie Stahl, 24, also of Twisted Knot, said she had been in "pretty much every building."
"There's a little spot outside where, if you get up early in the morning, you can see the sun rise," she said. "I just love it."
As the piles of sodden insulation grew higher and the drizzle intensified, the horde of volunteers headed off to lunch in a casemate beneath the ramparts. They were interrupted, however, by the squish of George Washington's boots.
The general - a.k.a. John Godzieba - arrived with a small entourage to encourage the volunteers and inspect the fort.
Washington received the cheers of the volunteers with suitable modesty and then headed off to inspect the damage.
As Washington walked through sodden rooms, Pat Jordan, president of the Olde Fort Mifflin Historical Society, stood on a balcony, shaking his head at the damage.
"This is one of those hurts," he said. "Like when someone dies."