This study focuses on one five-mile stretch of muddy ground connecting the Des Plaines and Chicago Rivers, in order to explore the continued importance of environmental factors and local geographies within the wider history of indigenous-European relations on the North American continent. Paying particular attention to how waterways and waterborne mobility influenced power dynamics between Native peoples and incoming Europeans, my research grounds imperial and indigenous histories of North America's borderlands in the local environmental context of encounter.Historians have long wrestled with explanations for indigenous-European relations, and eventual U.S. hegemony in the borderlands of North America. In recent years, interpretations for both cross-cultural collaboration and conflict have tended towards examining cultural misunderstandings and discrepancies in political power at the expense of exploring the environmental and geographic particulars which influenced interactions. This study seeks to amend that, demonstrating how contests over geography and local environments shaped the terms of encounter from early contact through the era of U.S. colonization of the American interior. By examining the Chicago portage—a key geographic link between the waterways of the Great Lakes and Mississippi drainage—the project illuminates the navigable waterborne world of the North American interior. Both Native peoples and Europeans traveled and labored on portage paths, connecting waterways to maintain geographic linkages between the Great Lakes frontier and the wider Atlantic world from the seventeenth century forward. When the maritime empires of France, and eventually Britain, entered the region, they too came to value portages as the geographic keys to navigating the North American interior. They adopted indigenous techniques of canoeing and relied on Native knowledge of local portage environments to extend maritime networks deep within the continent. But as United States officials arrived in the region in the 1790s, Chicago became a renewed site of contest. As U.S. officials grappled to extend their influence at Chicago through the 1830s, they faced a number of imperial and local challenges stemming from divergent interpretations of Chicago's geography. U.S. officials would only succeed in their conquest of Chicago by overhauling the landscape and its people in a two-pronged settler colonial subjugation of both the local environment and the Native peoples of the region.