Pennsylvania State Society

Children of the American Revolution

State Theme: Anchoring History

“Good citizens cannot be made suddenly. They must grow...” Harriett Lothrop, founder of the N.S.C.A.R.

Cheval de Frise

What it is

            For more than 200 years a strange object lurked undisturbed in the murky depths at the bottom of Delaware River, until last summer.
            The cheval-de-frise, which looks like a telephone pole with an iron point, was designed to protect Philadelphia from invasion by the British. In 1775, a series of chevaux-de-frise was sunk in the Delaware six feet below the surface, waiting to puncture the hulls of enemy ships.
            After the war the chevaux-de-frise were removed to allow river traffic to resume. However, this one was missed. It is in remarkably good condition because the water and mud created an anaerobic environment that prevented the wood from rotting and the iron tip from rusting over the last 200 years.
            This is the first Cheval-de-frise found in the Delaware since the 1940s. The other existing one is located at the Camden County Historical Society.
            Sunoco, the company who found the cheval-de-frise by sonar techniques, donated this historic find to the Independence Seaport Museum to ensure proper preservation and make it available to an audience.

Historical Background

            In the years leading up to the American Revolution, Philadelphia was the most important city in the colonies. As tension between the colonists and the British escalated, the Pennsylvania Council for Safety, headed by Benjamin Franklin, prepared for war.
            Robert Smith designed fortifications to protect Philadelphia from naval invasion. He modeled his design on chevaux de Frise, “Friesian horses,” land fortifications so named because of their use during the Siege of Groningnen in 1594.
            The location of the chevaux and the method to navigate around them was a closely guarded secret. Over sixty-chevaux de frise were sunk in the Delaware River during the years 1775-1777.

What it looks like

Smith’s design consisted of a large square or rectangular timber box or frame. Several logs with iron tips were attached to the frame, with their tips facing downstream in order to pierce the hulls of enemy ships. The frames were then sunk in the river and filled with stones so that the iron tips were several feet under water at low tide.
The cheval de frise (or the remains) is a long trunk of yellow pine, approximately 11 feet long and 18 inches in diameter, and then terminates in an iron point (the strap), 39 inches long and 22 inches wide. One side of the iron strap is parallel to the log; the other side is angled.

How it is being preserved

            The object was initially kept in a bath of a sodium carbonate solution with pH of approximately 8.5 in order to prevent further corrosion of the iron. The object was initially rinsed with water several times to remove surface dirt and grime and loose iron corrosion products.
            The iron was then removed to treat the wood. The iron is currently kept in a bath of sodium hydroxide solution.
      After necessary documentation, preparation, and stabilization, the object will be treated in PEG (polyethylene glycol), a common treatment for waterlogged wood.