A new book tells the story on the “triumph of capitalism” in the U.S. in the remarkable 35 years after the Civil War when the American economy exploded in size, becoming by far the largest, most productive and most technically advanced in the world. In 1860 the United States had imported almost all its steel — the product that was increasingly the measure of economic power at that time — from Britain. By 1900 it was producing more steel than Britain and Germany combined and exporting it profitably to both those countries. H. W. Brands tells this story of extraordinary economic transformation in “American Colossus.”