Volunteers with Friends of Rock Creek’s Environment collect trash in the park during a day of service in 2011 to honor late civil rights leader Martin Luther King Jr. (Ricky Carioti/The Washington Post)

In Washington, the Friends of Kenilworth Aquatic Gardens had to cancel its Martin Luther King Jr. Day of Service on Saturday because the partial government shutdown has the gates locked at the park along the Anacostia River.

The Student Conservation Association also postponed its service day on Monday at Washington’s Anacostia Park, where about 400 volunteers were registered to participate.

And in San Francisco, the Golden Gate National Parks Conservancy has canceled Martin Luther King Jr. Day service projects at five sites in and around the city.

Across the country, the shutdown has derailed some Day of Service projects that have become popular traditions over the King holiday weekend and that have provided needed support for sites run by the National Park Service.

The slain civil rights leader’s birthday was Jan. 15, when he would have turned 90, and his federal holiday is Monday.

King was assassinated in Memphis on April 4, 1968, by escaped convict and segregationist James Earl Ray.

Most King holiday service projects appear ready to continue as scheduled — in the D.C. area, for example, the District’s annual Peace Walk and Parade is set to kick off at 11 a.m. Monday from 2500 Martin Luther King Avenue SE, and there is a canvassing event in Columbia Heights, among other activities.

At the Bethesda North Marriott Hotel and Conference Center in Montgomery County, volunteers can participate in service projects benefiting “area nonprofits, educational sessions and information tables for individuals, families and groups,” according to a county news release.

Other events include an activity in Frederick, Md., where volunteers with the nonprofit Glories Hats Project can help make hats for terminally ill children and blankets for wounded veterans and chemotherapy patients.

But the absence of help at federal sites is a loss for the National Park Service, and a letdown for volunteers, project leaders said.

“It was disappointing from our standpoint because of the people we had to turn away,” said Karen Davis, senior vice president for advancement at the Virginia-based Student Conservation Association.

“It equates to a little more than 800 hours of service that they would have been putting in for the national park,” she said Thursday. “It’s one of our premier events that we do here in D.C.”

The event was postponed because the park’s staff, which is usually there to help out, has been furloughed, she said.

“It delays what needs to be done” for the park, including trash removal and clearing invasive plants, she said. “It’s disappointing.”

But she added, “We’ll be back.”

Still, the shutdown did not seem to reduce the number of sign-ups, Davis said. “It was on track with past years of the numbers that turn out for these type of service events.”

Samantha Jo Warfield, a spokeswoman for the federal Corporation for National and Community Service, which has not been affected by the shutdown, said of the anticipated turnout for service day: “I know of many projects that are already at capacity or have expanded their event to utilize more volunteers.”

“The nation’s volunteer rate has . . . remained remarkably stable for 15-plus years . . . [and] the D.C. area ranks in the top 10, about 10% above the national average,” she wrote in an email.

George Washington University had about 100 students lined up for a service day in the District’s Rock Creek Park before the shutdown, said Amy Cohen, head of school’s Honey W. Nashman Center for Civic Engagement and Public Service.

“We had it scheduled for a while, but we got notice pretty early on that we were not going to be able to work with them,” she said. “Once folks realized that the shutdown was really real, they let us know that we could not do that.”

“Generally, if we have a [service project] cancellation, we turn to the Park Service,” she said. “But they’re not able to take volunteers now.”

Cohen said the school has about 1,000 students and community members who will be volunteering elsewhere on other King service projects.

At Kenilworth Park and Aquatic Gardens, an enclave of quiet wetlands along the Anacostia River in Northeast Washington, the friends had to cancel their annual service day because the park is closed.

“It’s in­cred­ibly frustrating,” said Tina O’Connell, executive director of the friends group.

“The Park Service needs the help of volunteers and partners like friends groups to carry out its mission,” she said. “So with the shutdown, they’re not able to provide the services they do for all their visitors, and it makes it very difficult for us to continue to support them.”

“I think there are a lot of things people can do to support the national parks right now,” she said. “One is to support their friends group that belongs to the national park of their choice.”

DeNeen L. Brown contributed to this report.