This dissertation examines how the federal government asserted U.S. authority across the national territory after the Civil War. Central to this state project were campaigns for social reorganization at the nation’s peripheries. In both the postbellum South and West, U.S. officials sought to govern indigenous peoples and the formerly enslaved by reorganizing their labor, land, and social relations, thereby undermining struggles for social and political autonomy. Yet this project faced significant obstacles, such as federal institutions’ limited capacities, conflicts between those institutions, and opposition from diverse local populations. Through these struggles, a pattern emerged in which federal authorities forged connections to specific groups of northern capitalists and reformers, whose resources and social power enhanced federal projects to reorganize the South and West. Examining these dynamic relationships sheds light on the concrete social forces that yoked together southern Reconstruction, western imperialism, and industrial capitalism in the last third of the nineteenth century. These broad developments were evident in many forms, including in the trajectory of one company: Phelps Dodge, a mercantile-turned-industrial corporation based in New York City, which invested in southern lumber and western mining after the Civil War. Reconstructing Phelps Dodge’s social and political activities, this dissertation describes how northern elites worked with the Freedmen’s and Indian Bureaus to reorganize social relations at the peripheries. In doing so, it shows how elite northerners shaped the social orientation of the postbellum state, and how the state itself became a terrain of capitalist class composition on a new scale. These developments also influenced the postwar land policies that precipitated Phelps Dodge’s extractive enterprises. Policies to administer unenclosed timber and mineral lands accelerated a post-emancipation enclosure movement, which was oriented specifically towards industrial corporations like Phelps Dodge. As ex-slaves, Native peoples, and yeoman farmers struggled to defend their own practices of land and property, Phelps Dodge made private property surveillance a de facto department of corporate operations. This dissertation therefore describes how one structure of political economy ultimately prevailed over others, making it more and more difficult for freed, Native, and other dispossessed peoples to maintain alternative forms of life.