They once bristled with guns, missiles and thousands of fighting men.

Now battleships, the 20th century's lords of the waterways, are spending their retirements swarming with schoolchildren and tourists. Obsolete in the world of modern naval warfare, where aircraft carriers and guided missiles reign supreme, many older battleships have avoided being sunk or scrapped and are now living museums.

"They are such a unique part of nautical history," said retired Navy Capt. Don Hess, executive vice president and chief operating officer of the USS Missouri Memorial Association, in Pearl Harbor. "They've been the centerpiece of naval architecture for better than a century. There's a real interest in nautical history ... And battleships were such a big part of the 20th century."

It's well accepted battleships were integral to the U.S. military effort since the USS Texas' keel was laid in 1895, and "The Great White Fleet" circumnavigated the globe in 1907.

But following the attack on Pearl Harbor in 1941 and the Battle of the Midway the following year, it became clear the ships might not play as decisive a role as they had in previous battles. In the Korean, Vietnam and Persian Gulf conflicts, battleships were used mainly as floating batteries for shore bombardments.

The last active battleship, the USS Missouri, on which the documents ending World War II were signed, was decommissioned on March 31, 1992 to make way for high-tech missile cruisers and flattop aircraft carriers.

But old battleships don't just fade away, said retired Rear Adm. Thomas U. Seigenthaler, executive director of the Battleship New Jersey Memorial and Museum.

"The tremendous size and impact they're awesome," he said from his Camden, N.J., office. "It's not like walking aboard a destroyer or another kind of ship. It's totally inspiring to just look at the guns. They're very quieting, and instill a feeling of strength and power."

The Battleship New Jersey, which opened to the public in October, is nothing if not towering. The "Black Dragon," or "Big J," stands 11 stories tall, weighs 54,889 tons fully loaded and is the length of about three football fields. It housed 3,000 men during World War II and carried 16-inch turrets that could destroy targets 23 miles away.

Now it's floating on the Delaware River near the Walt Whitman bridge outside Philadelphia, and is boarded each day by as many as 2,200 visitors. Schoolchildren even  have weekend "encampments" there, where they spend the night onboard.

Some 10,000 kids have already run rampant on the Alabama battleship, which is part of a 155-acre park that also includes a submarine and 24 aircraft.

"We have overnight stays every weekend, a scavenger hunt, quizzes, things of this nature," said Bill Tunnell, executive director of the USS Alabama Battleship Memorial Park in Mobile, Ala. "It's a fun campout experience for the parents and the scouts."

What makes battleship memorials unique is that they're living memorials, said retired Capt. Dave Scheu, director of the Battleship North Carolina, in Wilmington, N.C.

"When you usually talk about a museum, you talk about a building inside which are artifacts or art," said Scheu. "But here, the primary building is the ship itself and what's interesting is that that's the prime artifact, this is an artifact in which other artifacts are housed."

Of the 48 naval ships of all nationalities serving as museums throughout the world, seven are battleship memorials.

But with such gargantuan memorials come the herculean labors needed to keep them in shape. The Alabama, for example, needs 500 gallons of paint for its exterior and 4,000 gallons to keep its interior fresh. And the budgets for the battleship museums often independent non-profit organizations are usually derived almost entirely from their admission fees and gift shops.

That means they can't count on governmental assistance to keep the ships, well, afloat.

"They are expensive," Tunnell said. "We normally spend everything we budget for, and we budget to spend everything we bring in."

The amount coming in every year can range from about $1.5 million for the North Carolina to $5 million for the Missouri.

And they're worth every cent, Siegenthaler said, especially when you consider that we're in an age when behemoths like the New Jersey have been replaced by automated missile cruisers that require a crew of only 90.

"They're the end of a breed," he said. "But the good thing is we're able to keep them up, and that makes it kind of a sweet ending to the story, rather than a sad ending."