Theodore Roosevelt towers above the trees, waving his fist mighty at the airplanes that disturb the silence of his island. They don't pay any attention.

Travelers who just took off from National Airport probably don't know that they're crashing a nature party. By Phil Jenny, supervisor of the 88-acre island that sits squarely in the Potomac, surely does. "There are always those jets making noise," he says. "That's why I read about this place being called a wilderness."

So let's concede that Theodore Roosevelt Island is not exactly a wilderness. But it remains a place nearby to walk a line between forest and waterside, to squidge in the mud and generally to get away from it all.

Three minutes after crossing a multi-lane bridge, the visitor confronts our 26 President, surrounded by some of his cornier quotes etched on granite slabs: "I want to see you game, boys, I want to see you brace and manly, and I also want to see you gentle and tender," proclaims one. The visitor cowers. Even the trees look respectful. It's just those damn planes.

The planes, of course, weren't always there and neither was old T.R. The island has had half a dozen other names and at least that many lives.

"It's gone from wilderness to intensive cultivation and is going back to wilderness," says Nan Netherton, a historian researching the island's past for the National Park Service.

John Smith first led an expedition up the Potomac to Little Falls, one year after he founded Jamestown, so he was the first white man to see it. But King Charles II deeded Analostan Island, so named for the nearby Analostan or Necostan (as in Anacostia) Indians, to the man who got Maryland, Lord Baltimore.

"Lord Baltimore never saw the island, just as he never saw anything in America," says Bob Lyle, curator at the Georgetown Public Library. "He was the classic absentee landlord."

Accounts vary about the island's next few years. The Masons, the upstanding family that peppered its name around Fairfax County, bought it in 1717 from Lord Baltimore, although there had been other inhabitants there in the meantime.

Son John built a summer home on "Mason's Island," planted the entire island with cotton and gardens, and even raised prizewinning sheep. The elite of turn-of-the-19th-century Washington flocked to Mason parties, arriving by boat or via a causeway Mason built from the northern end of the island.

But Mason's Island's downfall began, Jenny claims, once John Mason built the causeway and the island became more accessible.

Not only did the island change owners, it also changed function. It served as a training ground for Union troops during the Cigil War, and as a jousting ground after it.

And then it just sat. The mansion burned and the barracks crumbled. Boathouses built after the Civil War also met an untimely demise. Mason's sheep left long ago. The cattle that had been raised to feed the troops munched all the garden produce.

Enter Theodore Roosevelt.

Soon after his death, a group formed dedicated to securing a monument in his memory someplace in Washington. According to Netherton, Roosevelt fans and Thomas Jefferson canonizers locked horns over a certain piece of land in the Tida Basin. Well, no one goes to the Roosevelt Memorial to look at the cherry blossoms, so we know who won that one.

Instead, the association bought the island in 1931. "An island is more fitting for such a conservationist as Roosevelt," notes Netherton. "Even without the monument. Maybe especially without it." The monument was unveiled in 1967, after the Roosevelt family rejected a previous design, a large celestial sphere: "The globular jungle gym would desecrate the memory of anyone," Alice Roosevelt Longworth supposedly said.

"Most people don't come because it's dedicated to Roosevelt anyhow," says Jenny.

"In fact, most people don't come at all." The park averages about 100,000 visitors a year - which sounds like alot until you figure that thousands visit Lincoln Memorial daily in the summer.

Don't go to Roosevelt's Island expecting to find a nature center or a place to have a cook-out. The park planners have deliberately left the island to return to its natural state, and, besides weekend guided hikes, there are few planned activities.

But you might feel a bit proprietary after a few visits. One woman, now retired, comes daily and, according to Jenny, knows more about the wildflowers there than he does.

"There must be a psychology of islands," Netherton suggests. "When I tell people about my project, they tell me I'm writing about their island. But I feel like it's mine now." FINDING THE ISLAND

Get to Theodore Roosevelt Island by exiting from the northern lanes of the George Washington Parkway. Hours are 9:30 until dark. Every weekend at 11 and 2 one of the rangers leads a hike, telling about the nature or the history of the island. Call 557-8990. CAPTION: Picture, T.R. ON HIS ISLAND: A WELCOMING WAVE, OR A FIST WAVED AT THE JETS? By Mike Goergen.