YUMA — Dozens of construction workers labor like a bustling colony of ants — only this colony is located along a 126-mile-long portion of the United States's southern border with Mexico. Standing 100 feet from one of these construction sites, watching workers install the concrete-filled steel beams into the ground feels painfully slow, but driving along the banks of the river and canal, the workers' years of labor is overwhelmingly evident and compelling. The wall is up, everywhere. Workers decked in orange vests operate the yellow construction machines in a robotic fashion as they drop the maroon pieces of steel...