Overlooked here by the Sweet Grass Hills of northern Montana, the sleek little Milk River takes the measure of the Great Plains, as it flows from southern Alberta into the Missouri River and onward to the Gulf of Mexico.
But think how amazed Coronado would have been if he had somehow been able to sense the true extent and variety of North America’s grasslands. Little did he know that he had set foot on a vast prairie heartland—a continent of grass—that was flanked on every side by smaller islands of grasslands and prairie-to-forest transitions, or savannas. To the north, for instance, beyond his farthest imaginings, lay the Peace River Parklands, a region of rolling grass and poplars that marked the frontier between the Great Plains grasslands and the boreal forest. To the east, the Prairie-and-Oak Transition Zone—a tongue of prairie interspersed with groves of hardwoods—extended to the Great Lakes and beyond, marking the interface between the grasslands and the eastern deciduous forest. To the south, the prairies merged and melted into sultry, soupy marshlands to produce the semitropical vistas of the Western Gulf Coastal Grasslands. And to the west, in the broad valleys of the western Cordillera, lay the California Grasslands—spangled in spring by lupines and yellow-orange poppies—and the arid Palouse Grasslands of the Great Basin. Dominated by scraggly stands of sagebrush and spiky, sparse grasses, the Palouse, or bunchgrass, prairie stretched along the drainage of the Columbia and Snake rivers to intergrade with the shrubby growth of the Montana Valley Grasslands.
And in the center of everything there was the main attraction, the Great Plains Grasslands themselves, a landscape that even today invites wonderment. This truly is big sky country, with horizons that extend from the boreal forests of Alberta, Saskatchewan, and Manitoba to the deserts of the American Southwest and from the foothills of the Rockies to the Mississippi drainage. The numbers speak for themselves. Length: 1,500 miles (2,400 kilometers). Width: between 400 and 700 miles (between 600 and 1,100 kilometers). Vaguely triangular in outline, the region is broadest toward the north and narrows to its apex in the Hill Country of central Texas. Total area: 1 million square miles (2.6 million square kilometers), or roughly 14 percent of the entire land mass of Canada, Alaska, and the Lower Forty-Eight States.
> DEFINING TERMS
The word “prairie” entered the English language in the 1680s, when fur traders first began edging across the North American continent. Initially, the term was applied to the area just west of the Mississippi River, where the grasses often grew so tall that a man mounted on horseback could not see over them. Later, as the Europeans pushed farther westward, they found themselves in a country of short, spiky plants, quite different in appearance from the Mississippi grasslands. To mark this distinction, the arid grasslands of the western plains were often referred to as “steppe,” a word the explorers borrowed from Russian. The term “prairie,” or “true prairie,” was reserved for the grasslands that the traders knew best, the tall, waving grasses of the eastern plains.
Although biologists continue to find it useful to classify grasslands by height—as short, tall, or mixed—they have dropped the old idea of true prairie. In contemporary usage, the terms “prairie” and “prairies” refer to any expanse of land that is dominated by grass and other nonwoody plants. Prairies, simply put, are grasslands. With the addition of the definite article, “the prairies” also serves as a regional designation for the great grasslands that sprawl across the interior plains of North America.
The geographical terms that are used to define the plains also require clarification. Traditionally, geographers have divided the prairie region into two components: to the west, the Great Plains and to the east, the Central Lowlands. But because there is no clear geographical feature to separate these zones, the boundary between them has never been fixed with precision. On some maps, the dividing line cuts along the 100th meridian; on others, it shifts east to follow the curves of the Missouri River. In either case, the line divides the west from the east, separating prairie from prairie. Several recent sources, however— including the online Atlas of the Great Plains—have erased this artificial division and redrawn the map to show the grasslands of the interior plains as a coherent unit. In this book, the term “Great Plains” refers to the grasslands at the heart of the continent, as shown by the maps.
The Grand Geographical Tour
But length and breadth are not the only descriptors of the Great Plains. The prairies also have a vertical rise and run that add a whole other dimension of interest. Formed primarily by sediments that washed out of the Rocky Mountains millions of year ago, the landscape slopes away from west to east, stepping down from an elevation of roughly 1 mile (about 1,700 meters) above sea level at the base of the foothills to a few hundred yards (or meters) on the banks of the lower Missouri River. Often, the change happens so gently that you hardly notice it. Who would have imagined, for example, that the drive across Kansas, from west to east, following in Coronado’s path, would be downhill all the way and that you’d lose more than half a mile (one kilometer) in elevation while traversing that seemingly level state?
Overlain on this gently sloping plain are a surprising diversity of landforms. The geography of the Great Plains offers something for every taste, from fantastically sculpted badlands to craggy mountains to some of the flattest expanses of country anywhere on the planet. “I reached some plains so vast, that I did not find their limit anywhere I went,” our old friend Coronado exclaimed in a letter to the king of Spain in 1541, “with no more land marks than if we had been swallowed up by the sea. . . . not a stone, nor bit of rising ground, nor a tree, nor a shrub, nor anything to go by.” The landscape to which he was referring is now known to geographers as the High Plains, an elevated and sometimes spectacularly featureless tableland that extends from Nebraska and Colorado into northern Oklahoma and Texas. An erosional remnant of a high-and-wide landscape that once extended over much of the Great Plains, the region is bounded on three sides by dramatic cliffs, including the upthrusting wall of the Mescalero Escarpment in the west, the tree-clad Pine Ridge Escarpment to the north, and the amazingly convoluted and striated Caprock Escarpment in the east.
Formed by erosion sometime in the last 1 million to 2 million years, the spectacular red sandstone wall of the Caprock Escarpment forms a natural boundary between the High Plains of Texas and the rolling terrain of the Osage Plains to the east. In places, the escarpment towers as much as 1,000 feet (300 meters) above the surrounding country.
To the south of the High Plains lie the limestone hills of the Edwards Plateau, or Texas Hill Country—a world in itself—where the rolling countryside is broken by domed upwellings of rock, deeply cut by streams, and eaten away underground to form a honeycomb of sinkholes and caves. The Edwards Plateau, in turn, is bounded in the south by the terraced ridges and eroded canyons of the Balcones Escarpment, which slashes across Texas at the southern limits of the Great Plains grasslands.
To the northwest of the Edwards Plateau lies the broad Pecos Valley and a landscape of spectacularly eroded caverns, sinkholes, and steep-walled limestone cuts. And north of the Pecos are the shadowed moonscapes of the Raton Section, where mesas capped with lava compete for attention with contorted