Plains bison, Bison bison

      And in the center of everything there lay 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 landmass of Canada, Alaska, and the Lower Forty-Eight States.

       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 years ago, the landscape slopes away from west to east, stepping down from an elevation of about 1 mile (roughly 1,600 meters) above sea level at the base of the foothills to a few hundred yards above sea level 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 (a 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. See Map 3: Geography of the Great Plains.

      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 on 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 badlands and the burned-out cones of Capulin Mountain and other long-extinguished volcanoes. From there, it is on to the broad, terraced valleys of the Colorado Piedmont, literally “foot of the mountains,” where the waters of the Arkansas and South Platte rivers have, over millions of years, stripped away layer after layer from the original High Plains surface. (This dramatic, if localized, lowering of the surface explains, for example, why the road heading east out of Denver tracks steadily upward for the first half hour or so, as it climbs out of the South Platte floodplain and onto the surrounding High Plains benches.) The effects of water erosion can also be seen on the rugged Missouri Plateau and the deeply dissected valleys of the Plains Border region.

      If water has cut into these landscapes, wind has smoothed them out. For example, the southeastern edge of the Platte River valley is softened by a broad belt of curving, undulating sand dunes that were deposited by dust storms sometime during the Ice Age. Similar formations, shaped by similar forces, are also to be found strewn up and down the drier, western side of the Great Plains, from the Great Sandhills of southwestern Saskatchewan in the north to the Mescalero Sands of the Pecos Valley. And right in the middle of the map lies one of the prairies’ little-known natural wonders—the Nebraska Sandhills, a region of whale-backed, grassy rises and prairie wetlands that, at an area of almost 24,000 square miles (61,000 square kilometers), ranks as the largest field of sand dunes in the Western Hemisphere. These sandscapes were put in place by the relentless northwest winds that have been coursing across the landscape for millions of years.

      With so few barriers to stand in their way, these same winds have had the run of the entire Great Plains region. Although their influence can be seen in many parts of the country—for example, as ridges of windblown silt along both the South Saskatchewan and Upper Missouri rivers—their influence is most obvious in the eastern and southern regions of the Great Plains. These include not only areas of the Colorado Piedmont and the High Plains but also the “low plains” to the east, notably the rolling hills of the Plains Border country, the Osage Plains, and the Glaciated Central Lowlands. Much of this sweep of country is blanketed in deep, contoured drifts of fine silt, or loess—pronounced “luss”—another gritty, wind-borne by-product of glaciation. The result is a gently undulating landscape of soft, rolling hills and, in places, extraordinary bluffs, like the delightfully eroded and unexpected Loess Hills of western Iowa.

      The northern plains region, by contrast—north and east of the Missouri River, from Alberta to Manitoba and south through the Dakotas—is less apt to be buried in loess, but it nonetheless bears the imprint of the Ice Age. Here the terrain is an unmade bed of glacial rubble, or till, lying exactly where it dropped when the ice sheets retreated from the landscape thousands of years ago. And protruding above this jumble of knobs and kettles is an assortment of sprawling, flat-topped uplands, including Turtle Mountain, Wood Mountain, and the Cypress Hills, which straddle the boundary between past and present. Like miniature versions of the High Plains, they are the last surviving remnants of an ancient, preglacial landscape that has otherwise been lost to erosion.

      Finally, and most surprising of all, are the honest-to-goodness mountains that jut out of the northern plains, particularly on the unglaciated reach of country south and east of the Missouri River. From the glowering Black Hills to the jagged Crazy Mountains, they stand as a peak experience (if you’ll forgive the pun) for anyone who has been led to believe that the prairies are monotonous.

       THEN AND NOW

      IT IS ONE thing to send our minds running across the contours of the Great Plains Grasslands and their unexpectedly varied landforms. It is quite another