The Department of Licenses and Inspections demolished it without a hearing by the city Historical Commission - apparently violating ordinances protecting historic structures.
Historical Commission Director Richard Tyler said yesterday he had just learned the building had been razed and was looking into the matter. He confirmed that it had been an historically protected building.
L&I spokesman Thomas McNally said his department in September sent the Historical Commission a list of properties due for demolition that included the Cannonball House.
The building got its nickname during the 1777 effort by the British to take Fort Mifflin on the Delaware River from American forces. British guns were set up a mile away at the farmhouse.
For six days in November 1777, Fort Mifflin took a pounding from 250 British cannons firing thousands of shots in one of the heaviest bombardments up to that time.
Some historians believe it was the oldest house in Philadelphia.
When the Southwest Sewage Treatment plant needed space to expand in the 1970s, the building was ``saved'' by moving it to a piece of federal land outside Fort Mifflin donated by the Army Corps of Engineers.
The structure was never put on a foundation, but was left standing on I-beams.
From time to time, history buffs called attention to the house's precarious state.
In September 1994, L&I notified the city Office of Housing that the house ``was imminently dangerous'' and would be demolished unless repaired. The September demolition notice also was sent to the housing office, McNally said.
``It was really a significant building with its ties to the Swedes, Samuel Carpenter and the battle of Fort Mifflin,'' said John Haigis, an activist in historical preservation in Southwest Philadelphia.
Haigis recently had written Recreation Commissioner Michael DiBerardinis urging action to save the house. ``I got an answer simply saying there was no money to fix it up,'' he said.
Some Drexel University students were studying it as a class project to see if it could be salvaged and reused as a caretakers house, said Haigis, adding it could have been saved by spending $5,000 15 years ago.
Said Dori McMunn, executive director of nonprofit Fort Mifflin on the Delaware: ``I was really shocked when I saw it was demolished last Thursday. I expected it to fall down by itself someday.''
She saved a few bricks, wood molding, handmade square nails and other artifacts.