Tristan Dewar of Congress Heights, and his dog, Lamb Chop, find a quiet spot during last month’s Kingman Island Bluegrass Festival. More than 12,000 people attended; now, Kingman’s minders are imagining what’s next. (Andre Chung for The Washington Post)

Every year, thousands of Washingtonians, clad in flannels and duck boots, denim vests and Chuck Taylors, amble across a pair of rickety-looking bridges over the Anacostia River, bound for one of the city’s most confounding pockets of land: Kingman Island.

Even when the weather is soggy, the Kingman Island Bluegrass Festival is its namesake’s moment in the sun. Late last month, beneath a dove-gray sky and a light drizzle, the 45-acre isle exuded the charm of a lush secret garden, teeming with fiddlers, foot-stompers, banjo-pickers and the sort of rugged men who don’t visit rugged islands without their dogs in tow.

“I’m on Kingman Island, land of dreams,” a 20-something joked into his phone as he wove through the crowd. Others clutched hot coffees as they walked the island trail and cozied up on blankets to watch the bands.

It’s human nature to covet places like this, to tread all over them with expensive sneakers, to plant flags.

And as District officials (okay , developers) transform every corner of the city’s waterfront, Kingman and neighboring Heritage Island do increasingly look like the stuff of dreams: untamed green space near a Metro station and as far from new luxury apartments as you can get.

The island’s stewards, egged on by the success of the bluegrass festival, are dreaming up more reasons to come here. They imagine weddings on Kingman, more music festivals on Kingman, places for the public to put in their kayaks from Kingman, and rustic but elegant dinner parties with your favorite D.C. chef on Kingman.

It sounds idyllic. But can they pull it off?

A new floating dock allowed concertgoers to take a spin on the Anacostia. (Andre Chung for The Washington Post)

Others walked the trail from one stage to another. (Andre Chung for The Washington Post)

At the bluegrass festival, Jim Foster took concertgoers out onto the water in boats and watched their faces as they discovered the island, the river, the wild. Foster, who is the president of the Anacostia Watershed Society, an environmental group, says that when preservationists want to show off their part of the city, they now go after newcomers who have no preconceived notions about the Anacostia.

It’s working. In the festival’s first year, a few hundred people showed up for the then-free event. For this year’s edition, the seventh, 12,000 people found their way onto Kingman, with most forking over $25 to $35 for a ticket.

As concertgoers crossed the first bridge, they caught a clear view of Kingman’s big quandary, the thing that keeps the runners and the nature-seekers away: RFK Stadium.

For decades, Kingman’s fate has been intertwined with RFK’s. Just to get to the island, you have to park in the remotest and creepiest of the stadium’s many remote and creepy parking lots.

Once, there was nothing here. No RFK, and no islands.

In the early 1910s, the U.S. Army Corps of Engineers, dredging the Anacostia to make room for cargo ships, piled the accumulated muck into a long, narrow isle and its tiny, marshier little sister.

Since then, groups as diverse as the Army, the National Park Service and developers have struggled with what to do with the islands.

“Pretty much every decade, someone came up with a new plan,” says Alex Quarles, director of development for Living Classrooms, the education nonprofit organization that the city tapped to run Kingman.

For now, the tree-lined southern part of the island is used to teach city-reared children about nature. (The northern half became part of Langston Golf Course.)

Among the proposals was an airport. A nature center. A 9/11 memorial.

The most audacious idea of all, which was floated by an Italian contessa and bounced around for most of the 1980s and ’90s, would have turned Kingman into an amusement park called Children’s Island.

The neighbors were not amused, environmentalists even less so, Congress intervened, and Children’s Island was ultimately tossed onto the Kingman trash heap.

After the Redskins’ departure from RFK in the mid-1990s, Kingman grew as desolate as the stadium. By the 2000s, “we were finding a couple of bodies a year out there,” says Steve Mutschler, managing director of Living Classrooms.

“Access is so horrible,” Foster says. “We’ve done such a great job of separating people from the river. You’ve got [Route] 295, you’ve got RFK. Everything is scaled for the automobile. It’s not like you’re going to take a walk to the river and check it out.”

Last month, Events DC, the group that controls RFK, floated new proposals for the future of the stadium grounds. Major League Soccer’s D.C. United, which has been playing at RFK Stadium for two decades, will also vacate the facility, perhaps as soon as 2018.

The proposals reimagine what’s possible on the 190-acre stadium campus: Maybe a new sports venue, and maybe not. But the islands are clearly in the plans. In the renderings are pedestrian bridges to Kingman, an amphitheater on the waterfront, an “urban beach” on the banks of the Anacostia near the islands.

Greg O’Dell, president and chief executive of Events DC, insists that the proposals for the islands are very early suggestions and have sustainability in mind.

But ideas such as a waterfront stage may be at odds with the natural, ragtag feeling of Kingman that was on full display during the bluegrass festival, when bands set up amid the rocks and beneath tents next to a sea of beech trees. The last thing Living Classrooms wants is for the island to be another Jiffy Lube Live.

“Building an amphitheater to do community programming and a place for kids to sit — great,” Quarles says. “Building an amphitheater so you can have really loud concerts every single night and charge people $50 is not what we want.”

RFK Stadium looms over Kingman and Heritage islands. Its redevelopment could affect the man-made isles. (Andre Chung for The Washington Post)

It’s not lost on those who look out for the Anacostia what a gem Kingman could be.

“We’ve told people for two generations, ‘Don’t go there,’ ” Foster says. “And you know what? They don’t go there.”

But the festival shows that they might, particularly D.C. newcomers who are used to parks and trails wherever they came from.

It could be just what they’re missing. It could be their island.