Once there was a place called Smeltertown, and it was known as the largest industrial city on the banks of the Rio Grande. The smokestacks of the American Smelting and Refining Company, which polluted the air for three miles in every direction, grew so tall over the decades that they became a landmark just inside the El Paso side of the US-Mexico border. In a community of small adobe houses, many with dirt floors and without indoor plumbing, both...