The Border Wall Is Back

Photographs by Philip Cheung

At Coronado National Memorial in Arizona, the demolition crews blowing up national-park land tend to announce explosions at least a day in advance, as a warning for hikers to stay away. The crews have been working their way up the western slope of the park for the past couple of months, right along the international boundary with Mexico. President Trump’s border wall needs a smooth, straight path, and there are mountains in the way.

Trump didn’t build along...