President Donald Trump and Congress failed to reach an agreement on a spending plan by midnight Friday, triggering a partial shutdown of the federal government. In the past quarter-century, the government has partially shut down three times -- and far more often in decades past.
U.S. troops will stay at their posts and mail will get delivered, but almost half of the 2 million civilian federal workers will be barred from doing their jobs if the shutdown extends into Monday.
The U.S. military will continue to fight wars and conduct missions around the world, including in Iraq, Syria and Afghanistan. And members of the military will report to work, although they won't get paid until Congress approves funding.
But Defense Secretary Jim Mattis warned Friday that a shutdown will have far-reaching effects.
"Our maintenance activities will probably pretty much shut down," he said during remarks at the Johns Hopkins School of Advanced International Studies. "We do a lot of intelligence operations around the world, and they cost money. Those, obviously, would stop. And I would just tell you that training for almost our entire reserve force will stop."
And, while ships will remain at sea and airstrikes against enemy fighters will continue, any National Guard forces heading out to do weekend training duty around the country will arrive at armories and be told to go home.
Shutdowns have led to furloughs of several hundred thousand federal employees, required many government activities to be stopped or curtailed and affected wide swaths of the economy.
During Jimmy Carter's administration, shutdowns happened nearly every year, averaging 11 days each. During Ronald Reagan's two terms in the 1980s, there were six shutdowns, typically just one or two days apiece.
Here's a look at recent shutdowns, their causes and impact:
— October 2013. Sixteen-day partial shutdown, which came as Tea Party conservatives, cheered on by outside groups, demanded that language to block implementation of President Barack Obama's health care law be added to a must-do funding bill. Then-Speaker John Boehner, R-Ohio, tried to avoid a shutdown by funding the government piecemeal, but the effort faltered.
The shutdown affected most government operations and resulted in the furlough of 850,000 employees, costing the government 6.6 million days of work and more than $2.5 billion in lost productivity, according to a report by the Congressional Research Service. Boehner survived the shutdown but stepped down two years later amid conflict with the hard-right House Freedom Caucus.
— December 1995-January 1996. Republicans led by then-Speaker Newt Gingrich, intent on slashing the budget, forced a three-week shutdown in a bid to coerce President Bill Clinton to sign onto a balanced budget agreement. Republicans were saddled with the blame, but most Americans suffered relatively minor inconveniences such as closed parks and delays in processing passport applications. The fight bolstered Clinton's popularity and he sailed to re-election that November.
— November 1995. Five-day shutdown after Clinton vetoed an interim spending bill to block Medicare premium increases. Led to longer shutdown a month later.