For three years and more the question of whether or not to build a wall along the U.S.-Mexican border has been a central issue of American politics.
Building a wall, and having Mexico pay for it, was a central commitment of candidate Donald Trump during the 2016 presidential campaign. The failure of Congress to appropriate funds for a wall, after Mexico refused to do so, was the catalyst for the longest government shutdown in American history only last month.
Even after more than $1 billion in new funds had been appropriated for border security, the imperative of building the wall was the pretext for President Trump's Feb. 15 declaration of a state of national emergency, and the re-direction of over $6 billion in additional money to wall construction.