Parts of the American government have shut down, which means more than 700,000 government workers have to go without work or pay.
It happened because of a dispute between the two main political parties - President Obama's Democrats and the Republicans.
They can't agree on how the country should be funded for the next year, and had until midnight on Monday 30 September to decide whether a budget plan should be passed.
As it was not passed this means many government-funded services have no money to keep running.
What happens now?
Essential workers like air-traffic controllers and border guards will still work, but museums, National Parks and top tourist attractions like the Statue of Liberty will close, and many government workers will stay at home.
The defence department said uniformed members of the military will continue on normal duty, but that large numbers of civilian workers will be told to stay home.
On Monday evening, President Obama made sure that military personnel would be paid, despite the shutdown.
The government will meet again on Tuesday to try and reach an agreement.
Why did this happen?
Like our political parties here in the UK, Democrats and Republicans stand for different things.
But the biggest thing they can't agree on is how America should spend its money for the next year.
It's left the US extremely divided.
Governments of countries collect money from the public in tax - and then have to decide how that money should be spent in the country.
The biggest sticking point in the US right now is how much government money should be spent on healthcare.
No NHS in the USA
The UK has a National Health Service (NHS). It's funded by the government using money raised through taxes, which all working people above the age of 18 must pay, and means that people don't have to pay each time they use a doctor.
Unlike the UK, the United States doesn't have an NHS.
For everyone apart from the poorest, who get some support for medical treatment, visiting the doctor or hospital in America can be very expensive - and the main way to bring down the cost is health insurance.
People pay a sum of money each month so that if they need to go to hospital, the insurance company pays the bill. Many big companies provide this to people who work for them, but there are millions of people without insurance.
President Obama and the Democrats want to introduce a new healthcare system into the United States, which they believe will make healthcare more affordable for most Americans.
It's called the Affordable Care Act - nicknamed 'Obamacare' - and was made law in 2010, though much of it hasn't come into force yet. For the law to work, all Americans have to take out health insurance - in the past it's been optional.
At the time 26 of the 50 US states challenged it in America's Supreme Court (the top court in the land). They claimed that it was illegal to make everyone have health insurance.
The court narrowly decided that the Act would stand, but the Republican party continues to fight against the Affordable Care Act, saying it costs too much government money.
They also don't believe that it's right for people to be forced to pay insurance.
And because of this, the Republicans didn't want to sign the budget plan for the next year, as it included putting the Affordable Care Act into practise - which is something they don't want.
Because the two sides couldn't agree before the midnight deadline yesterday America is now in shutdown mode - meaning only limited services are operating.
What happens next?
The shutdown will continue until the two parties agree on a resolution, which could last anything from a day to a few weeks.
This situation has happened many times before - one time in 1995, the federal government was closed for 21 days.
Eventually lawmakers should come to a compromise that gets things back on track as the longer it goes on for, the more the American economy will struggle under the pressure.