RICHMOND, California (Reuters) - The battleship USS Iowa, which served the United States through victory and tragedy during six decades at sea, set off on its final voyage on Saturday, a trip to Los Angeles to become a museum.

With a cheer, volunteers in hard hats cast off the last of a dozen thick lines that had moored the 175-foot-tall gray dreadnought in the Port of Richmond. Then it slipped slowly into the San Francisco Bay, towering over the three tugboats that pulled it.

Throngs of onlookers gathered as the ship sailed under the Golden Gate Bridge.

It was a sentimental send-off for the Iowa, which saw service in the U.S. Navy conflicts around the world before being decommissioned in 1990 and sold to the nonprofit Pacific Battleship Center in May 2010.

The Los Angeles Harbor Commission voted unanimously on May 17 to create a permanent home for the ship at the city's port, where it will drop its gangplank to the public on July 7.

As the Iowa headed into San Francisco Bay, spectators swapped tales of the Iowa's storied past. It carried the late President Franklin Roosevelt across the Atlantic to his historic meeting with Winston Churchill and Josef Stalin in World War Two.

The battleship was equipped with a special bathtub for Roosevelt - who was partially paralyzed following a bout with polio - and it remains on board.

Later in the war, the Iowa pounded beachheads in the Pacific with its 16-inch guns ahead of Allied landings and took part in the Japanese surrender in Tokyo Bay in 1945. During the Korean War in the 1950s, it conducted gun strikes and bombardments.

Not all memories from the Iowa are so triumphant. An explosion in one of its gun turrets killed 47 sailors in 1989. The next year, the Navy consigned the Iowa, along with its other three remaining battleships, the Missouri, Wisconsin and New Jersey, to its reserve fleet.

ONE OF THE LAST OF ITS KIND

"There's no more ships like this in existence in the active navies anywhere in the world," said Robert Kent, president of the Pacific Battleship Center. "They've either been sunk, scrapped or turned into museums and the Iowa is the last battleship to find a home."

Dozens of volunteers spent months refurbishing the Iowa for its final role, including at least three men who served on it.

"It's been a greater privilege than I can express," said David Canfield, 42, who was first assigned to the Iowa in 1987 at the age of 17 as a non-rated fireman.

Canfield, who was aboard the Iowa for the 1989 explosion, joined Marty Palmiere and Michael McEnteggert in reminiscing about life on the Iowa. They talked of hitting golf balls into the sea and of having "steel beach" picnics on its decks.

"A lot of memories are here," McEnteggert said before the three scrambled aboard for one last ride.

The Iowa was decaying as politicians tried to determine its future. Some of the gun turrets had been removed and the radar tower dismantled.

"Paint was peeling, rust was everywhere," said Bob Rogers of the Pacific Battleship Center. "A lot of metal was rusting through so it was really important for us to save her."

The state of Iowa donated $3 million and private sources and loans provided another $1.5 million to the refurbishment. Rogers estimated that those contributions, along with 25,000 volunteer hours and donated supplies and equipment add up to $7 million.

The goal was to restore the 887-foot ship not to its condition when first commissioned in 1943 but to its appearance when armed with contemporary weapons such as Tomahawk missiles for its second commission in 1984 after spending the previous 26 years in mothballs.

Despite the extensive repairs, the Iowa could not steam to Los Angeles under its own power because the contract with the Navy forbade it, Rogers said. The Navy did not want a ship of this power fully operational outside of its control.

The Iowa was to proceed down the coast of California at rate of about 6 miles per hour, a fraction of the 38 mph it could make in its heyday.