WASHINGTON (AP) -- Barriers came down at federal memorials and National Park Service sites and thousands of furloughed federal workers -- relieved but wary -- returned to work across the country Thursday after 16 days off the job due to the partial government shutdown.
Among the sites reopening were Yosemite National Park in California, the Smithsonian Institution's network of popular museums, and the World War II memorial in Washington, which had been the scene of protests over the shutdown.
"Just to be able to get back to serving the public is so important," said Greg Bettwy, preparing to return to work with the Smithsonian's human resource department.
For other returning workers, shutdown-related frustration turned to elation at being back on the job. Some confronted backlogs of email and paperwork; others voiced concern that a gridlocked Congress might trigger another shutdown in January.
"The phrase everyone is talking about is 'kicking the can down the road,'" said Richard Marcus of Silver Spring, Md., who has worked at the National Archives and Records Administration for 29 years. "We'd hate to have to live through this all over again."
National Park Service Director Jonathan Jarvis said all 401 national park units -- from Golden Gate National Recreation Area in California to Acadia National Park in Maine -- were expected to reopen Thursday. The reopenings include tour roads, trails, visitor centers and other facilities at the park sites. Educational programs will resume, and permits will again be issued for special activities, Jarvis said.
Also reopening are dozens of programs that preserve nature and historic sites and improve access to outdoor recreation in local communities. And the U.S. Forest Service started lifting a ban on national forests. American Forest Resource Council President Tom Partin said national forest campgrounds would reopen as soon as employees could visit to make sure they're clean and safe.
The federal workers who were furloughed or worked without pay during the shutdown will get back pay in their next paychecks, which for most employees come Oct. 29.
At the Labor Department, Secretary Thomas Perez greeted workers with an email telling them he understood how much the furlough disrupted their lives.
"Unfortunately, as President Obama correctly noted, you are occasionally called on to perform your remarkably important work in a climate that too often treats federal employees and contractors as a punching bag," Perez said.
The Defense Department called back about 7,000 furloughed civilians. In an open letter to the workforce, Defense Secretary Chuck Hagel said the department still faces budget uncertainty as Congress struggles to pass a 2014 spending bill and deal with automatic budget cuts. Pentagon Comptroller Robert Hale said Thursday that the department lost at least $600 million worth of productivity during the four days that civilians were furloughed.
The National Institutes of Health also will see lingering after-effects -- NIH warned university scientists not to expect a quick resumption of research dollars.
"As the shutdown drags on, the challenge of re-establishing normal operations quickly is growing," NIH Deputy Director Dr. Sally Rockey emailed researchers.
Workers at U.S. Citizenship and Immigration Services restarted the computerized worker verification system, e-Verify. The system used by business owners to verify the legal status of workers was the only USCIS program affected by the shutdown.
In Washington, the Capitol's visitor center planned to resume tours Thursday, the United States Holocaust Memorial Museum was reopening, and the Smithsonian -- overseer of many of Washington's major museums -- proclaimed on Twitter, "We're back from the (hashtag)shutdown!"
The National Zoo was set to reopen Friday, though the popular panda cam went live Thursday morning -- giving fans a view of a cub wriggling about as her mother, Mei Xiang, tucked her paws under her chin and watched.
At the National Institute of Standards and Technology in Gaithersburg, Md., email servers were slowly grinding back into gear.
Fire protection engineer Dan Madrzykowski had been in the office for about half an hour, and about 800 emails had popped into his inbox, but that covered only back to Oct. 13. Still, Madrzykowski said he was pleased to be back at work. "Nothing good was coming from keeping the government closed," he said.
Patrice Roberts, who works for the Department of Homeland Security, said she wasn't prepared for the emotional lows of the past 16 days.
"It's just frustrating having that kind of control over your life and just having it taken away from me," said Roberts, who is expecting another shutdown in January. "I'll be better prepared next time."