"We're going to build a wall..."
We have heard President Trump speak this line countless times since his presidential campaign.
But why is building a wall so important to the United States president?
Here are the facts you need to know about the wall and what its construction means to the people of the United States.
I would build a great wall, and nobody builds walls better than me, believe me, and I'll build them very inexpensively. I will build a great great wall on our southern border and I'll have Mexico pay for that wall.
Building a wall was one of Donald Trump's key promises when he was campaigning to become president.
It was an idea that divided the country, but won Donald Trump many supporters.
And now, two years into his presidency, he wants to deliver on that promise.
A wall at the border between the US and Mexico would be designed to prevent people from entering the United States illegally.
Currently, there is a total of 650 miles of barrier along the border which is 1,900 miles long.
However, Donald Trump believes this is not enough to turn away people attempting to cross the border.
In a televised speech, he stated, "All Americans are hurt by uncontrolled, illegal migration."
"We are out of space to hold them and we have no way to promptly return them back home to their country," he continued.
President Trump wants to build a 1,000 mile wall made out of steel to prevent people from crossing the US-Mexico border.
He believes the rest of the terrain along the border should be enough to prevent people from attempting to cross.
But building a wall of this size is going to cost a lot of money.
We are not paying for that stupid wall.
Originally he suggested that Mexico should pay for the wall - but it was soon very clear that the Mexican government would not pay.
Now, President Trump is appealing to his own government and therefore, to US taxpayers, to pay for the wall.
He estimates that he would need $5.6 billion (the equivalent to £4.4 million) to build a steel barrier across the border.
This appeal has not been well received by the opposing party - the Democrats.
The issue of how to pay for the wall has caused a standoff within Congress - the body which creates, debates and makes laws in the United States.
With no decision being made, Congress have been unable to pass a spending bill - essentially agreed budget for the United States government.
And with no officially agreed budget for the government, it's been forced to partially close.
It is likely it will stay partially closed until a solution to building the wall can be found.
Some have suggested that a barrier is immoral. Then why do wealthy politicians build walls, gates and fences around their homes?
Polling shows that most US citizens don't agree with building the wall.
A mid-November CBS poll found that 59% disagree with building the wall.
However, those that agree with the wall being built are working hard to make their opinions heard.
Immigration - particularly illegal immigration - is a very important issue to many Americans.
Those who agree with the wall being built believe that the United States is overwhelmed by illegal immigration.
Their opinion is that people who come to live and work in the country, without official permission from the United States government, are taking advantage of the United States' privileges and freedoms.
Many feel the wall will prevent illegal immigrants from coming into the country as easily.
...too many illegals are taking advantage of the United States taxpayers with no means of ever contributing to our society.
A GoFundMe page has been set up by US Army veteran Brian Kolfage. He believes that in the event that Congress refuses to pay for the wall, Donald Trump's supporters could pay for it instead.
"If the 63 million people who voted for Trump each pledge $80, we can build the wall." he states on his fundraising page.
Already he has raised nearly $20 million. A long way off the $5.6 billion needed, but still a very large amount to raise.
But what about the majority of citizens who do not believe the wall is a good idea?
The symbol of America should be the Statue of Liberty, not a 30-foot wall.
A majority of US citizens believe that the wall is a bad idea or that it shouldn't be a priority for the President.
The Democratic Party, who are in opposition to President Trump's Republican party, believe that building the wall is wrong.
"President Trump has appealed to fear, not facts. Division, not unity," stated Democrat Senator, Chuck Schumer, in reaction to Trump's televised address.
There is some evidence that the statements Trump made during his address were not factually correct.
For example, President Trump has claimed that there is a crisis in the number of people attempting crossing the border illegally in the past few years.
But statistics show that the number of arrests at the US-Mexico border have decreased a lot since the early 2000s.
Currently, there is an average of 400,000 arrests at the border each year, compared to more than a million arrests in the early 2000s.
There were, in fact, 1.6 million arrests made by Border Patrols in the year 2000.
Aside from the questioning of the facts, many Democrats feel that building a wall would send the wrong message about immigration to the United States.
Senator Schumer referenced the Statue of Liberty as a better symbol for the United States.
The Statue of Liberty is also known as The Immigrant's Statue, as it was seen as a representation of hope and welcome to the millions of people who emigrated to the United States through New York more than a century ago.
But this does not mean that the Democrats are completely against more security at the border between the US and Mexico.
They have stated they would support increased security, but not in the form of a wall and not in the form of a budget of $5.6 billion.