BOSTON (CBS/AP) — The USS Constitution, the world’s oldest commissioned warship still afloat, has returned to Boston’s waters.

“She is the oldest warship afloat in the world. She is the oldest sailing vessel in the world that can sail under her own power and she is the beginning of the United States Navy,” said Margherita Desy, a historian at Naval History & Heritage Command Detachment Boston.

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The undocking of “Old Ironsides” on Sunday marked the end of restoration work that started two years ago, officials said. A celebration was held at the USS Constitution Museum.

“By doing this restoration project, we’re ensuring that we’re going to continue to on being a part of the Navy, a part of the fleet,” said Robert Gerosa, the Constitution’s commanding officer.

The wooden ship was launched in 1797 and earned its famous nickname notching victories in the War of 1812.

“The ship has been the cornerstone of the Navy for a long time,” said Gerosa. “To be a part of the ship is truly an honor.”

The restorations extend the life of the nearly 2-feet (61-centimeter) -thick vessel — the last remaining survivor of six ships created when President George Washington signed the Naval Armament Act — said Desy.

“We still have the mission of telling the Navy’s story and representing the more than 322,000 sailors that are on duty, on watch around the world, as we speak right now,” said Gerosa.

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A crowd of people gathered around the ship Sunday night to watch as the ship was floated off its blocks and into the harbor.

The ship, which turns 220 in October, enters dry dock about every 20 years for below-the-waterline repairs. The most recent work included replacing 100 hull planks and installing 2,200 new copper sheets, 500 of which were signed by nearly 100,000 museum visitors, according to USS Constitution Museum President Anne Grimes Rand, who called the ship “a wonderful symbol for our democracy.”

“It was meant to last for 10 or 20 years, and to have (the) ship here more than 200 years later, it needs constant care,” Rand said.

The Constitution entered the dock at the historic Charlestown Navy Yard on the night of May 18, 2015, and on Sunday — a day that was expected to have the highest tide of the summer — the dry dock at the navy yard was flooded, and the ship was lifted off the keel block.

When the height of the water at the dry dock equaled the height of water at the Boston Harbor, the ship was slowly towed out of the dock.

The vessel will be temporarily docked at a nearby pier to undergo more restoration work until September, when it will re-open for public tours.

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)