This essay revisits the incorporation of the West into the economic orbit of the United States as a contested and contradictory process, formative for the trajectory of American capitalism and analogous to turbulent transitions that took place in other peripheral regions in the world economy at the end of the nineteenth century. It examines the formation of a national economy as a controversial economic and political project that pitted eastern capitalists against western populists, who sought to harness the influx of investment into the region in the service of their own vision of regional development. First, the essay explores the case of the financial elite of Boston, the second-largest financial center in the United States, and this cohort’s deliberate efforts to redeploy capital toward new ventures in the trans-Mississippi West. It sketches the growth of the Boston-owned stockyards of Kansas City, illustrating the capacity of eastern financiers—like financiers elsewhere around the world at the time—to reinvent major industries, establish new urban centers, set large populations in motion, and revolutionize the ecology of entire regions. Second, the essay interrogates the intimate links between the migration of capital from the eastern United States and the emergence of western political institutions. It analyzes contentious constitutional conventions throughout the West—in Colorado, Montana, Wyoming, Idaho, the Dakotas, and Washington—that occasioned the transformation of these federally controlled territories into semi-sovereign states. The analysis focuses on three of the key economic issues that best crystallize the problem of political jurisdiction in an interconnected economy—water rights, corporate regulation, and industrial relations—and then, in more general terms, on the three themes of distribution, legibility, and spatiality.