From the Arctic to the South China Sea, states are vying to secure sovereign rights over vast maritime stretches, undersea continental plates, shifting ice flows, airspace, and the subsoil. Conceiving of sovereign space as volume rather than area, the contributors to Voluminous States explore how such a conception reveals and underscores the three-dimensional nature of modern territorial governance. In case studies ranging from the United States, Europe, and the Himalayas to Hong Kong, Korea, and Bangladesh, the contributors outline how states are using airspace surveillance, maritime patrols, and subterranean monitoring to gain and exercise sovereignty over three-dimensional space. Whether examining how militaries are digging tunnels to create new theaters of operations, the impacts of climate change on borders, or the relation between borders and nonhuman ecologies, they demonstrate that a three-dimensional approach to studying borders is imperative for gaining a fuller