Once each spring, not long after the ospreys return and the wetland grasses become tinged with green, Kingman and Heritage Islands come alive — with bluegrass music.

The annual Kingman Island Bluegrass and Folk Festival draws up to 10,000 people to the oft-forgotten green oasis that sprawls between the two shores of the Anacostia River near Washington, District of Columbia’s RFK soccer stadium. Attendees bring lawn chairs and sunscreen, and sprawl in the sun for an afternoon of live music that is the biggest fund-raiser for the Living Classrooms Foundation, which maintains the islands.

And many of those bluegrass fans, after tasting what these islands have to offer, return to experience their quieter sides.

“For me, the island is such a hidden gem,” said Michael Macrina, director of development for Living Classrooms and organizer of the annual festival. “Using the resources we have and this festival has become a great platform for educating the community and getting them out there.”

The islands weren’t always an inviting place to visit. The U.S. Army Corps of Engineers dredged these islands out of mud flats in 1916 because the flats were thought to be a breeding ground for mosquitos. (The mosquitos, however, are still here.) The idea was that the new islands would become a public park, a swath of green in the middle of a burgeoning capital city.

The northern half of Kingman Island became Langston Golf Course, a National Park site that was important to African American golfers because it was open to them during the segregation era.

But, without the funding to create an official park, the rest of the space languished and became the dumping grounds for not only trash but also a series of far-flung ideas for its development.

Airports and amusement parks were proposed over the years to make better use of the city-owned land. Residents fought the proposals, but many still treated the islands like a trash heap, discarding old appliances in the overgrown brush.

In 2007, the city selected Living Classrooms, a foundation that educates youth and young adults in the outdoor environment while improving it and the community, to head the islands’ restoration.

Living Classroom’s Green Team, composed of at-risk youths in need of job skills, has been at work on the islands ever since. The team uses machetes to beat back the invasive plants that have overtaken parts of the island, and install native ones in their wake. Team members have cleared trails where there were none and removed hundreds of pounds of trash that had become woven into the landscape.

As they’ve peeled back the layers of neglect, an oasis of wildlife has emerged in the heart of the city. Ospreys and bald eagles circle overhead and make nests on the islands. Egrets and blue herons wait amid the newly planted wetland grasses — fenced off to keep geese from destroying them — for their breakfast to swim by.

The islands have become a favorite bird-watching haunt for former DC Mayor Anthony Williams, who took a special interest in the Anacostia during his term. More than 100 species of birds have been identified on and near the islands.

Today, beavers build dams and foxes excavate holes here. Swamp flowers bloom and towering trees provide shade. A growing number of people also stop by to take the island in by bike, boat and on foot.

“There’s a misconception that the Anacostia is so dirty and polluted and unhealthy that there aren’t things living in it. That’s not true,” said Matt Boyer, former managing director of Living Classrooms in the District.

For those who have that perception of the Anacostia River — or who have kayaked down its expanse after a heavy rain and seen the trash washed in with the storm — these islands are another place entirely. While much of the river has benefitted from work to restore its wetlands and wildlife, these islands have received special attention.

They are an example of what restoration can accomplish, both for occasional visitors and to the residents that live nearby. A big part of Living Classrooms’ work is to use the restored spaces to educate local children about their impact on the environment.

Bryant Curry, Green Team coordinator, uses the islands to explain to schoolchildren where their trash ends up when they throw it on the streets or into a gutter.

“That’s something they don’t know and don’t understand, that literally something I put on the ground can end up in the river,” he said.

The two islands, which are part of the Chesapeake Bay Gateways and Watertrails Network, offer more than 50 acres of natural habitats that can be explored via a growing, 1.5-mile trail system or from the water.

Unlike many access points to the Anacostia River, this one boasts plenty of parking on its southwest entrance in RFK Stadium Parking Lot 6. The park is also accessible by metro and bike.

By car, visitors enter the park’s gates and can walk or bike across the footbridge that spans Kingman Lake to the islands. The first island from this entrance is the smaller Heritage Island. A trail that winds around the perimeter of Heritage Island is a good place to start, offering water and wildlife views along the way.

The footbridge continues on to Kingman Island, where the trail continues to the north and south, but is not a loop. The trail connects to Benning Road to the north, not far from a BikeShare rental hub for those who didn’t bring their own set of wheels.

For avid bicyclists, the Kingman Island trails are part of a growing network called the Anacostia Water Trail. Construction is under way to bridge gaps in the trail that will run the length of the Anacostia River in DC.

For now, experienced bicyclists can make their way to and from the islands on wheels by winding through a mix of urban and wild landscapes.

Visitors to the islands by boat can explore the park’s shore to the east on the Anacostia River and to the west on Kingman Lake. The boardwalk that sprawls across the islands features a dock access with stairs.

Living Classrooms is working to add other access points to the water, including a soft boat launch, although some visitors have already found ways to launch their kayaks and canoes without one. The nearest official boat launch is at Bladensburg Waterfront Park to the north.

While boating in or biking along the water is encouraged, swimming or eating fish from the Anacostia River is still considered unhealthy. Boaters should also be aware of the time of day and the tides while navigating the Anacostia’s tidal waters. The marshes around Kingman Island can change water levels up to 3 feet twice a day, so boaters could easily get stuck in the mud at low tides.

Picnics are permitted on the islands, as are dogs on a leash — owners are asked to pick up after their dogs. Photography and wildlife viewing are encouraged. Visit the Kingman Island website, www.KingmanIsland.org, to learn more about the types of wildlife identified on the islands.

Kingman & Heritage Islands

Kingman and Heritage Islands Park is open 9 a.m. to dusk April through October and 9 a.m. to 4:30 p.m. November through March. The park may be closed during normal operating hours in inclement weather or on national holidays. Check the park website for details on park closures.

Admission to the park is free.

The main entrance for Kingman and Heritage Islands Park is found on the west bank of the Anacostia River. This entrance is located at the back of RFK Stadium Parking Lot 6, approximately 0.1 miles south of Benning Road NE. A second pedestrian entrance is located at Benning Road. The approximate address of the entrance to RFK Stadium Parking Lot 6 is: 575 Oklahoma Ave. NE, Washington DC, 20002.

For details about Kingman & Heritage Islands Park, e-mail kingmanisland@livingclassrooms.org, visit www.KingmanIsland.org or call 202-557-1925.

For details about other sites in the Chesapeake Bay Gateways and Watertrails Network, visit www.baygateways.net.