Youngstown, Ohio, and the surrounding Mahoning Valley supplied the iron that helped transform the United States into an industrial powerhouse in the nineteenth century. The story of the Mahoning Valley's unorthodox rise from mid-scale iron producer to twentieth-century "Steel Valley" is a tale of innovation, stagnation, and, above all, extreme change. Located halfway between Pittsburgh and Cleveland, the Mahoning Valley became a major supplier of pig iron to America's biggest industrial regions. For much of the nineteenth century, outside consumers relied on the Valley's pig iron, but this...