The Eagle — the only tall ship on active service in the U.S. military — docked in Manhattan on Thursday to help celebrate the 226th birthday of the U.S. Coast Guard.

The three-mast, 295-foot-long vessel sailed into New York Harbor with Old Glory flapping at the stern, and its crew and 200 cadets proudly on deck. A marching band on board played patriotic tunes.

To the delight of spectators, the Eagle, its 20 sails fluttering, was tethered next to the USS Intrepid aircraft carrier at Pier 86. Summer in the City campers from the Bronx were at the dock to welcome the sailors.

“I am so happy to see the boat,” exclaimed Maimouna Doumbia, 7.

“It made me feel joyful, and I liked the flag,” said Sharon Altamirano, 8.

For all its splendor, the Eagle isn’t a native American. The ship was built by the Nazis as a training vessel 80 years ago and was seized by the Allies during the final months of World War II.

Since the war prize first arrived in New York waters in 1946, it has served as the Coast Guard’s floating classroom for cadets undergoing officer training.

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“It’s an incredible ship, and the cadets learn navigation right here at the chart table, and learn the fundamentals of star navigation,” said the ship’s captain, Matt Meilstrup.

Rear Adm. Jim Rendon, superintendent of the Coast Guard Academy in New London, Connecticut, said the mission of the Eagle “is to educate, train, develop and inspire leaders of character and service.”

Carly Holton, 25, a senior crew member from Sacramento, California, said work on the tall ship demands a sharp focus. In pulling the vessel to the dock, for example, a “heave ho!” call spurs crew and cadets into action.

“It’s to get everybody in line to pull. It’s all about teamwork and it demands a lot from everybody,” he said.

The hull and decks are made of steel. The original mahogany paneling in the captain’s dining and sitting rooms has been preserved, along with the mahogany tables. But hanging from a wall is something that didn’t come from the Nazis: a portrait of Alexander Hamilton.

The public is invited to tour the ship this weekend for free.

Cadet 2nd Class Brandon Williams, 19, of Wasilla, Alaska, described what it’s like to climb the Eagle’s main mast — nearly 15 stories high.

“You feel free when you are up there,” he said. “You can see 40 to 50 miles away. It’s amazing.”