Chapter 8 (“‘All That Vast Region of Grass Land’”) explores changing northern grasslands cultural geography, with sections on the transnational U.S. and Canadian Northwest, Northern Great Plains, Arid West, Prairie Provinces, and Middle West, labels all circulating in the middle of the twentieth century. This generation studied the environment, including works by geographers, scientists, and historians, who drew lines of aridity, weighed topographic influences, and charted ecology. They used “prairie” and “plains” interchangeably to express a sense of place, even as nationally distinct regional labels developed across the international boundary. Middle West expanded west into the U.S. northern grasslands (only idiosyncratically in Canada) as Corn Belt agriculture expanded. The division of the northern grasslands by a line of aridity into the West and Middle West derives from a settler-colonial mindset rooted in commercial agriculture. The choice to elevate annual precipitation over grass is as much a cultural as a natural way of dividing space.