Four years after archeologists overseeing excavation of the former World Trade Center site uncovered an ancient sailing ship, the mysteries of the old wooden vessel are finally unfurled.

Scientists at Columbia University's Lamont-Doherty Earth Observatory who study tree rings have determined the ship's frame was constructed out of white oak taken from an old growth forest in the Philadelphia area and probably cut around 1773, a few years, of course, before the official start of America's war for independence from Britain.

The intriguing conclusions, included in a new study published in the journal Tree Ring Research, strongly relied on earlier wood samples taken two decades before from Philadelphia's Independence Hall by Lamont scientist Ed Cook, whose work revealed tree growth rings still visible in the hall's timbers matched those from the World Trade Center ship, suggesting that the wood used in both structures came from the same region, said a university news release.

As trees grow, their seasonal growth is recorded by their generations of outer layers, which, when a tree is cross-sectioned, appear as rings.

Aside from detailing a tree's annual growth, the rings also reveal the climate in which the tree lived, with tighter rings indicating dry years and wider rings wetter periods.

The climatic indicators serve more or less as a tree birth certificate, showing scientists where pieces of wood originated.

Researchers say the ship has been tentatively identified as a Dutch-designed Hudson River Sloop, used to carry passengers and cargo over shallow, rocky water.

The vessel was likely built in Philadelphia, which was a center for ship-building in Colonial times.

It's believed that after 20 to 30 years of service, the ship was moored in lower Manhattan, a block west of Greenwich Street.

Over the many years, as trade in New York harbor and the young country grew and Manhattan's western shoreline pushed westward, the ship ended up buried by trash and other landfill.

Then, by around 1818, the ship might have vanished completely from view -- until the terrorist attacks on Sept. 11, 2001, led to the WTC site's excavation and ship's eventual rediscovery.