A remarkable piece of scientific detective work has revealed the wooden ship found beneath the wreckage of the World Trade Center was built just before, or during, the American War of Independence. Even the location where the wood was grown appears to have been settled.

In 2010, when digging the foundations for the buildings that will replace the twin towers, workers found a 9.75m long oaken partial hull 7m below what is now street level. Hickory in the keel indicated the ship was almost certainly of North American origin, but its age and specific place of construction were initially a mystery.

Isotopic dating isn’t precise enough to tell us the age of the wood from which the ship is made, so instead researchers from Columbia University used the tree rings. As they report in probably the most attention grabbing story ever published in Tree-Ring Research the rings in timber from different parts of the ship were found to be highly similar.

Lower Manhattan Development Corporation Via Columbia University. The rings in the white oak of the ship's hull reveal the seasons in which the timber grew.

Since the width of tree rings depends on the weather that season, trees growing nearby tend to have ring patterns that match each other fairly closely. When compared to 21 trees of the same species (white oak, Quercus Leucobalanus) from the eastern American seaboard team, led by Dr Dario Martin-Benito, found exceptionally good matches to those from the Keystone State.

“Our results showed the highest agreement between the WTC ship chronology and two chronologies from Philadelphia and eastern Pennsylvania,” the paper reports. The last rings indicate the ship was built from trees felled in 1773, confirming previous theories.

While the ship has potential to provide insight into construction of the day, the authors note “idiosyncratic aspects of the vessel's construction [indicate] that the ship was the product of a small shipyard.”

"Philadelphia was one of the most — if not the most — important shipbuilding cities in the U.S. at the time. And they had plenty of wood so it made lots of sense that the wood could come from there,” Martin-Benito told Livescience

The wood has previously been found to have been infested with Lyrodus pedicellatus, indicating a trip to the Caribbean at some point. This infestation with shipworm may have led to its premature demise, possibly being used as a sort of reclamation process to bolster Manhattan's defenses against the sea.

Although considered part of the World Trade Center site, the location of the ship was not excavated when the original towers were built.