In this Age of Organization between 1870 and 1900, the United States grew into a global industrial power. Transcontinental railroads spurred this breathtaking transformation, linking regional markets into a national market for manufactured goods; at the same time, railroads themselves served as a massive new market for raw materials, new technologies, and, perhaps most important, steel. Building on advantages developed over the course of the nineteenth century, the Northeast and the Midwest led the way in the new economy, while efforts to industrialize the South met with uneven success. Men like Andrew Carnegie became both the heroes and the villains of their age. They engaged in ruthless practices that would lead some to label the new industrialists “robber barons,” but they also created ingenious systems of industrial organization and corporate management that altered the economic landscape of the country and changed the place of the United States in the world.