And they weren't the only travellers to fall foul of the shutdown. If there was a symbol of America's pent-up frustration with a gridlocked political system, it was this: scores of elderly second world war and Vietnam veterans pushing past barricades to honour their fallen comrades at a memorial closed by a government shutdown.

The veterans arrived in Washington from Mississippi and Iowa, having spent thousands of dollars to charter "honour flights" to the capital. But like those of many others across the country, their plans collided with the reality of a Congress frozen by ideological disputes and unable to agree on how to keep the government open.

Lawmakers helped the veterans get past the barriers, but others around the country were not so lucky as tourists were blocked from their destinations and more than 800,000 federal employees were told to stay at home.

Cleveland Faggard, 89, who had been an aviation machinist for the Navy, had helped push past a black metal blockade after about a dozen Republican members of Congress arrived, responding to e-mailed pleas from the veterans. "I was just praying to the Lord," Faggard said. "He took care of it."

Around the country, barricades and padlocks closed off access to federal facilities as the vast machinery of the federal government began systematically shutting down operations for the first time in nearly two decades.

Employees feared they could be out of work for weeks, and many of them were angry. "Once the mortgage payment comes around and I don't get the pay cheque, it's going to be a problem," said Sherilyn Garnett, 44, a federal prosecutor from California. "It's stupid. It's really stupid."

In Washington, Tina Miller, who works in law enforcement for the federal government, said the shutdown would have a wide impact. "It's going to have effects for everybody and the community, everything. I'm not sure why they wouldn't think of that."

Americans seeking public services at federal buildings found the doors shut, with no indication of when they might reopen.

When Sheila Caraway, 23, arrived at the Internal Revenue Service office in downtown Los Angeles, she was turned away by a security officer who explained that parts of the government had been shut down. She left the IRS without the tax refund that she had hoped would help pay for her cable television bill.

"This is crazy. I don't like it. It's been over a year and I haven't gotten my refund," Caraway said, explaining that she had not followed the recent political struggles in Washington. "I think everyone is crazy right now."

Among the most noticeable impacts of the first shutdown of the internet era: many complex government websites were suddenly replaced by one-page notices like the one at Census.gov, which declared that "due to the lapse in government funding, census.gov sites, services, and all online survey collection requests will be unavailable until further notice."

Government Twitter accounts also went dark, although Twitter users helped fill the void with jokes and memes about the failings of their politicians.

The reality of the shutdown began to become clear early on Tuesday. Children's playgrounds in small pocket parks around Capitol Hill were closed. The military service academies suspended all intercollegiate sports competitions. The National Zoo's online "Panda Cam" stopped showing images of Mei Xian's latest cub. Officials stopped giving tours of Alcatraz prison in San Francisco Bay.

Those looking for data to assess the impact of a shutdown will have to do it without help from the Congressional Budget Office and the Census Bureau - both are closing. The Bureau of Labour Statistics is also closing and said its monthly jobs report would probably be postponed.