In a single lifespan in the late nineteenth and early twentieth century, America passed through an extraordinary economic and social transformation. Industrialization, urbanization, immigration, and westward expansion into the vast interior of the continent yielded the structural framework of the modern America we still recognize more than a century later. The roles played by financial capital, labor, and technology in this story have been widely examined. Less well understand, however, is the remaining puzzle: how did America generate the human capital necessary for this transformation? How...