But, two and half years after he took office, supporters – who were so enamoured by the idea, they regularly chanted in favour of the structure – may be forgiven for wondering where exactly it is.
Now, it has emerged that not a single new stretch of border wall has been built since Mr Trump took office in January 2017.
A statement released by the US Customs and Border Protection (CBP) agency confirmed the 51 miles of fencing completed since Mr Trump took power has simply replaced barriers that already existed.
No original wall or fencing has been created in areas that previously did not have any, it said.
That is despite the fact that a total of 205 miles of both new and replacement wall and fencing has already been budgeted for since Mr Trump took office – including via the Treasury Forfeiture Fund which the president redirected through controversial executive action in February.
Speaking anonymously to the Washington Examiner, a senior official in the Trump administration said engineers could move faster on so-called replacement projects than entirely new stretches of fence because the approval process for environmental and zoning permits was less extensive.
Another official blamed Democrats for obstructing progress. He told the newspaper: “The wall projects are moving along as quickly as practicably possible given the unprecedented obstruction from Democrat lawmakers to protect and prolong open borders.”
Yet it seems the lack of progress will not deter Mr Trump from making the wall a central part of his 2020 election campaign.
When crowds took up their now familiar refrain of “build that wall" at a recent rally in El Paso, Texas, Mr Trump responded by telling them: “Now, you really mean 'finish that wall,' because we've built a lot of it.”
The CBP recently said it will be continuing to build the approximately 205 miles of wall that have been funded so far this year, using Treasury Forfeiture Fund money that Mr Trump seized in February after the partial government shutdown.
The Trump administration was sued for taking $6.6bn from the military and other departments to be used for building the border wall after Congress refused to grant the president the money he had requested.