Between 1880 and 1920 the US economy rode several transformative technologies into a new economic era.The transportation and communication revolutions that began earlier in the nineteenth century gained momentum: rail networks grew astronomically, and the telephone accelerated the communications revolution that the telegraph had begun. Meanwhile, although the corporate form as a legal entity was well established by 1880, it was in the years leading up to 1920 that very large, nation-spanning business enterprises came to dominate the economy. The cause was those famous Chandlerian twins, scale and scope.1 Corporations as a legal category were well known by 1880; but large, vertically integrated corporations as the prime mover of a rapidly expanding economy took over after that. This is the story of the corporatization of the American economy.