My dissertation tracks the various spatial visions of empire with which Spanish officials conjured el Septentrión as part of the Viceroyalty of New Spain and the global commodity circuits of the Spanish empire. I argue that this northern region (el Septentrión) was conceived as a vast amphibious space that encompassed continental North America and the North Pacific as one continuous territory. Understanding this América Septentrional requires bringing the Pacific into histories of Colonial Latin America. By doing so, my work highlights the breadth of an already globalized world to shift our understanding away from a predominantly Atlantic—and European—facing notion of the colonial period. Rooted in more than fifteen months of archival research in Spain, Mexico, and Canada and funded by the Social Science Research Council and Canada’s Social Sciences and Humanities Research Council, my research follows the itinerant lives of Spanish agents—missionaries, naval captains, merchant-capitalists, frontier military officers, and colonial administrators—whose thoughts about, and movements through, continental North America and the North Pacific made a vast territorial expanse imaginable as a manageable and exploitable geographical entity. Their views, though conflicting, coincided in interpretations of el Septentrión as an underused space (a periphery) with great potential to become a key node in Spain’s global empire.