The USS Constitution, the world’s oldest commissioned warship afloat, is undergoing a two-year restoration that started last week. Launched in 1797 in Boston, “Old Ironsides” is the ultimate achievement of 18th-century technology, says Northeastern Distinguished Professor of History William Fowler, who is an expert in maritime history and the history of Boston.

Fowler shared these five interesting facts you may not know about the vessel:

The birth of the U.S. Navy

The USS Constitution was one of the original three vessels built that launched the United States Navy. Built in Boston, the vessel took three years to complete and the $300,000 price tag was well above the $100,000 originally appropriated.

A name fit for a president

President George Washington selected the name Constitution for the frigate. He chose from a list of names supplied by Secretary of War Timothy Pickering. Other suggestions included President, Congress, Defender, and Liberty.

Good as new

The last time the USS Constitution underwent a restoration was in the 1990s. Fowler estimated that 10 to 15 percent of the vessel is still the original live oak used in the initial construction. Most of that is located along the keel because it has been submerged in salt water for hundreds of years and never exposed to the elements.

Return to Boston

In the late 1890s the USS Constitution was docked in Portsmouth, New Hampshire, and served as a barracks ship. That is until Congressman John “Honey Fitz” Fitzgerald, the grandfather of President John F. Kennedy, decided it was time to bring it back home to Boston, where it has been ever since.

The pride of a city

Fowler noted the city of Boston should be very proud to call the USS Constitution its own. “She is basically the equivalent of a nuclear aircraft carrier of the 18th century, the best of the best,” Fowler said. “Boston should be particularly proud because we built her and she’s still here.”