This is what we know about this mysterious artifact.

It was part of a ship. The timbers of the ship were made of white oak, and examination of the wood’s rings suggest that the timbers were harvested sometime around 1773, from somewhere near Philadelphia. The ship also contained some hickory, which grew only in eastern North America and Asia. From these facts scientists have deduced that the ship was almost certainly built in Philadelphia, which at the time was the most important shipbuilding city and center of commerce in colonial America. Moreover, the ship was probably made from the same source of wood that went into the construction of Independence Hall, where the Declaration of Independence and the U.S. Constitution were signed.

The ship made commercial runs to the south. We know this because the vessel’s timbers had been damaged by holes burrowed into it by Lyrodus pedicellatus, a type of “shipworm” typically found in high-salinity, warm waters like those in the Caribbean.

The ship met its end at the southern tip of Manhattan. Oysters attached to the timbers suggest that it floated in New York harbor for some time before it went to the bottom.

It was found in 2010, during the excavation for the foundation of a new building. Workers had already found lots of items at the site that suggested they were digging through an old landfill: animal bones, ceramic dishes, bottles and dozens of shoes. Most of this useless stuff was cast aside, but when the backhoe struck a 32-foot oak beam, construction stopped while scientists carefully removed the timber and took pieces of it to the Maryland Archaeological Conservation Laboratory for preservation, and to Columbia University’s Lamont-Doherty Earth Observatory for analysis.

And that’s how we know that an 18th-century American commercial vessel ended up in the basement of the most noteworthy commercial buildings in the world, the original World Trade Center.

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The ship survived less than 30 years. The center lasted for 28 years.

But now, with the excavation and construction of the Freedom Tower, both of these symbols have risen again.

Ships sink. Skyscrapers fall.

But strength endures.