It has for years, and the fingerprints all over it aren‘t Trump‘s but the Clintons‘—both Bill‘s and Hillary‘s…. Twenty-one years before Trump’s wall-building promise (and seven years before the 9/11 attacks), the U.S. Army Corps of Engineers began to replace the chain link fence that separated Nogales, Sonora, in Mexico from Nogales, Arizona, in the United States with a wall built of rusty landing mats from the Vietnam and Persian Gulf wars. Although there had been various half-hearted attempts at building border walls throughout the twentieth century, this was the first true effort to build a barrier of what might now be called Trumpian magnitude.