USS Constitution, newly restored, is returning to the water

The USS Constitution setting sail in 2012. (REUTERS/Jessica Rinaldi, File)

The USS Constitution, the world's oldest commissioned warship still afloat, will return Sunday to Boston's waters.

The undocking of the "Old Ironsides" will mark the end of restoration work that started two years ago, officials said. A celebration will be held at the USS Constitution Museum.

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

The USS Constitution guided into a dry dock in Boston, in 2015. (AP Photo/Charles Krupa)

"The ship has been the cornerstone of the Navy for a long time," said Robert Gerosa, the Constitution's commanding officer. "To be a part of the ship is truly an honor."

The restorations extend the life of the nearly 2-feet-thick vessel -- the last remaining survivor of six ships created when President George Washington signed the Naval Armament Act -- said Margherita Desy, a historian at Naval History & Heritage Command Detachment Boston.

Hundreds gathered about the ship Sunday afternoon as workers prepared for its return to the water, The Boston Globe reported. The ship is set to be floated off its blocks around 10 p.m. and into the harbor around 11:30 p.m.

The ship 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 expected to have the highest tide of the summer --the dry dock at the navy yard will be flooded, and the ship will be lifted off the keel block that night.

When the height of the water at the dry dock equals the height of water at the Boston Harbor, the ship will be pulled out of the dock.

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