Prototype U.S.-Mexico border walls stand in this aerial photograph taken over San Diego, California, U.S., on Monday, Oct. 30, 2017. President Donald Trump has directed the Department of Homeland Security to carry out one of his more prominent campaign promises: to build a wall on the U.S. border with Mexico. In October, signs of progress emerged—a handful of 30-foot-tall prototypes at a construction site near San Diego. Photographer: Daniel Acker/Bloomberg (Bloomberg)

From the very start of his campaign for the U.S. presidency, Donald Trump has passionately promoted construction of a border wall between the U.S. and Mexico -- and insisted that Mexico would pay for it. He remains determined to get something built, even if it’s not as vast as he initially envisaged. Ever since Mexico refused to foot the bill, the wall’s funding has been ensnared in budget negotiations in the U.S. Congress.

1. Why a wall?

Trump, in his many public statements on immigration and border security, has said an “impenetrable” wall would “stop dangerous drugs and criminals from pouring into our country.”

2. What might the wall look like?

Though Trump denies changing his position, he no longer seeks a monolithic, 30-foot-tall concrete wall stretching for more than 2,000 miles (3,218 kilometers). An administration proposal early in 2018 called for a more modest 722-mile mix of wall and fencing, mostly updating what’s been in place for decades, while relying on drones and other methods to secure the rest.

3. What’s been done so far?

Trump has insisted on Twitter and in other public comments that “tremendous amounts of wall have already been built” in San Diego and elsewhere. Fact-checkers point out that while some existing fence is being renovated, it is not the new concrete wall that Trump has promised. Something that has been built is a set of eight wall prototypes in a desert outside San Diego, California -- four of them primarily concrete, two made mostly of metal and two others being hybrid designs of concrete, metal bars and steel plating. The mock-ups were tested for their ability to repel attempts to climb over, smash through or tunnel underneath. U.S. Customs and Border Protection has said no single winner will be selected; rather, each prototype will “inform future border wall design standards in some capacity” -- once there’s money.

4. How much would a wall cost?

Estimates range from $8 billion to $67 billion or more, depending on whom you ask and the number of miles of wall that would be built. Trump’s fellow Republicans in Congress have said they expect a wall to cost from $12 billion to $15 billion, based on the cost to rebuild existing border fencing covering a third of that distance, though those projections don’t include the cost of buying non-government land. Based on Trump’s 2017 budget request for $2.6 billion to plan, design and build 75 miles of wall, Democratic Senator Claire McCaskill’s office estimated the per-mile cost would be about $37 million, or nearly $67 billion for the entire 2,000-mile border. A July 2018 report by the U.S. Government Accountability Office warned that the wall might “cost more than projected, take longer than planned or not fully perform as expected.”

5. How much money has Congress pledged?

Almost $1.6 billion so far, though not for a new wall. That funding includes $641 million for 33 miles of “pedestrian fencing” in the Rio Grande Valley in South Texas, $251 million for 14 miles of replacements for barriers in San Diego, plus money for enforcement. As part of negotiations over fiscal 2019 spending, Trump has asked for at least $5 billion; Democrats have offered $1.375 billion for new and replacement fencing. Trump has threatened to reject a funding measure needed to keep parts of the government running past Dec. 21 if he doesn’t get wall construction money.

6. How could Trump get Mexico to pay for the wall?

Outgoing Mexican President Enrique Pena Nieto and President-elect Andres Manuel Lopez Obrado have both emphatically refused to fund the border wall. Trump has suggested that the U.S. can recoup wall expenses from Mexico via alternative methods, including by cutting its trade surplus with the U.S. He’s also floated the option of invoking the Patriot Act to cut off or tax remittance payments to Mexico from Mexican immigrants living in the U.S. Mexicans sent home $25.7 billion in remittances in 2016, according to Banco de Mexico.

7. So who will pay for it?

If Mexico can’t be made to pay, U.S. taxpayers, most likely.

8. How much wall exists already?

Barriers span 653 miles of the U.S.-Mexico border, mostly along the western half. Much of the southern borders of California, Arizona and New Mexico have existing barriers, ranging from 18-foot-tall iron fencing and corrugated metal to makeshift vehicle barriers and barbed wire. Of the remaining thousand-plus miles of border land, two-thirds is private or state-owned, much of it in Texas. The Trump administration could seek to use eminent domain to seize land needed for a border barrier, as well as support roads and other infrastructure, though it would likely face costly legal challenges that could delay construction for years.

9. Would a wall even work?

Most experts doubt that a physical wall would do much to reduce illegal drugs pouring into the country each year. As part of a set of tools to combat illegal immigration, however, physical barriers could help. Israeli Prime Minister Benjamin Netanyahu praised Trump’s plan, saying a fence built along Israel’s border with Egypt has been a “great success” in keeping out migrants, mainly from African nations.

--With assistance from Erik Wasson and Jack Fitzpatrick. Cary O’Reilly contributed to an earlier version of this story.

To contact the reporter on this story: Mark Niquette in Columbus at

To contact the editors responsible for this story: Sara Forden at, Paula Dwyer, Laurence Arnold

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