Grassland is one of the four major vegetation types (or biomes) of the Earth, along with forest, savanna, and shrubland (which includes desert). Grasslands, which thrive in arid to subhumid conditions where ten to thirty inches of rain fall annually, easily contend with drought and ﬁre because their root systems are extensive and hardy. Grassland of one kind or another once covered about forty percent of the United States. The largest area is found in the American Great Plains, stretching from the tallgrass prairies of the Midwest to the mixed-grass and shortgrass prairies that run to the foothills of the Rocky Mountains. West and south of the Rockies sparser grassland proliferates in the Sonoran and Chihuahuan Deserts and the Great Basin of Nevada and Utah. It was not long ago that bluestem and Indian grass rippled horse high from horizon to horizon in many of these areas, frightening and astonishing early settlers with its oceanlike vastness. Richard Manning in his book Grassland suggests that the Rocky Mountains are islands in a sea of grass, an archipelago rather than a boundary or dividing line. This apt metaphor speaks to the surrounding endlessness of grasslands, whether they are the Russian steppes, African veldt, Argentine pampas, or English downs. The tallgrass prairie of the Sheyenne National Grassland is part of the nearly 1.3-million-acre system of the Dakota Prairie Grasslands that straddles North and South Dakota and also includes the Little Missouri, Cedar River, and Grand River National Grasslands.