This is a scientific and historical account of the cheatgrass invasion. Cheatgrass (Bromus tectorum) is an exotic species that appeared in North America in the late nineteenth century and has since become a dominant plant in the arid and semiarid rangelands between the Sierra Nevada, Cascades, and Rocky Mountains. It is the first grass to appear after the region's long, cold winters and thus has become an important forage plant for livestock and wildlife...