For a few hours of the first day of the first federal government shutdown in 17 years, the actual shutting down of national landmarks appeared to be proceeding slowly.

The Lincoln, Jefferson and other memorials on the Mall were still accessible to tourists as the sun rose and the sky lightened, with the fountain at the World War II Memorial flowing for all to see. The National Zoo’s Panda Cam continued to operate as well, offering viewers a look at giant panda Mei Xiang cradling her month-old cub.

But the camera went dark about 8 a.m., and visitors were soon blocked from the Lincoln Memorial by bicycle barriers that had been set up at the bottom of the plaza steps. Other landmarks were shut a short time later.

Signs posted on the barricades read: “Because of the federal government shutdown all national parks are closed.”

A spokeswoman for the National Park Service said that all the memorials on the Mall — including the Franklin D. Roosevelt and Martin Luther King Jr. memorials, as well as the Washington Monument — would be blocked over the course of the morning.

In addition, maintenance workers will shut off the 45 fountains that dot the Mall memorials and other attractions within the park system, said the spokeswoman, Carol Bradley Johnson.

Johnson said the new pumping and filtration system at the Lincoln Memorial Reflecting Pool would also be shut down.

More than 300 Park Service workers on the Mall would be furloughed during the shutdown, Johnson said. Workers have been told to report for duty Tuesday morning and stay for four hours to help shutter operations.

“We are pre-staging barricades,” she said, meaning that workers were delivering barricades to the various sites to be set up now that the government has shut down.

“We’re also contacting anybody who has a permit to let them know that in the event of a shutdown, all permits will be canceled,” she said.

One organization that will feel the impact of a shutdown is the Honor Flight program, which flies World War II veterans from around the country to Washington for a one-day visit to the memorial.

“We have been getting quite a few calls from honor flights and have had to let them know that the memorial will be closed and the fountain will be off, that the Mall is legally closed,” Johnson said. “So, unfortunately, they won’t be able to access the memorial.”

“Jefferson will be closed,” as well as “MLK, FDR, Ford’s Theatre, Korea, Vietnam,” she said, referring to various Park Service sites. “There’s going to be signs saying that they’re closed, and they will be probably blocked off. We’re limited in how much fencing we can get.”

Arlington National Cemetery, which is operated by the Army, will be open, but the cemetery’s Arlington House, run by the Park Service, will be closed.

Renda Overbo, D.C. volunteer coordinator and board member for Honor Flight Chicago, said her organization has a group of 90 World War II veterans and 45 volunteer guardians and medics scheduled to fly to Washington on Wednesday.

Their plan was to visit the World War II Memorial, where a ceremony with a color guard, the sounding of taps and the singing of the national anthem would honor the veterans.

Her group is checking whether the airline will let it reschedule. “As you know, these World War II veterans are 85-plus years old,” Overbo said. “So, if we schedule it again for next year, they may not be around to come and visit.”

Of the 90 Chicago-area veterans, “probably 70 are in a wheelchair or may need a wheelchair before the end of the day,” she said. “So, you can imagine the logistics of all this.”

The veterans “will be greatly disappointed” if the visit doesn’t happen, she said. Many veterans count such a visit among the best events of their lives. “It’s a major event,” she said.

Mary Pettinato, founder of Honor Flight Chicago, said: “They are so excited about the trip and about their chance to see the memorial that was built in their honor.”

“We have doctors,” she said. “We have nurses. We have paramedics. All of the logistics, the food, everything has been ordered and planned for six months now. This is a huge undertaking.”

She said she had not yet told the veterans that the trip might be off: “But they’re calling every 30 seconds.”

“It’s a logistical nightmare,” she said.

“It’s embarrassing,” she said of the government stalemate. “It really is. It’s embarrassing for both sides. When it comes to the memorials and the men and women who fought for our country, they should be sacred, and [veterans] should be allowed to see the memorial when they can.”