The Llano Estacado, commonly known as the Staked Plains but perhaps more accurately interpreted as the "palisaded" plains in geological terms, is the southern extension of the High Plains of North America and lies south of the Canadian River in northwest Texas and northeast New Mexico. A high mesa sloping at a rate of approximately ten feet per mile toward the southeast, it is one of the largest tablelands on the continent. This high flat land is located approximately between 101° and 104° west longitude and 31° and 35° north latitude. It is distinctly bounded on the north by the southern escarpment of the Canadian River valley and on the east by the irregular and deeply incised Caprock escarpment. The western boundary is the Mescalero Escarpment east of the Pecos River valley of New Mexico. The southern end of the plateau lacks a distinct physical boundary; it blends into the Edwards Plateau, and the Johnson Creek branch of the Colorado River, east of Big Spring, is probably best considered its boundary. The Llano Estacado comprises all or part of thirty-three Texas and four New Mexico counties and covers approximately 32,000 square miles, a larger area than all of New England. It is part of what was known to early explorers and settlers as the Great American Desert, a semiarid region with average annual precipitation of eighteen to twenty inches. The soils are almost universally dark-brown to reddish brown sands, sandy loams, and clay loams.
The Llano Estacado was first described by Francisco Vázquez de Coronado in a letter to the king of Spain in October 20, 1541: "I reached some plains so vast, that I did not find their limit anywhere I went, although I travelled over them for more than 300 leagues . . . with no more land marks than if we had been swallowed up by the sea . . . . there was not a stone, nor bit of rising ground, nor a tree, nor a shrub, nor anything to go by." United States Army captain Randolph B. Marcy, who led an expedition to explore the headwaters of the Canadian and Red rivers in 1852, echoed Coronado's impressions of the region: "It is much elevated . . . very smooth and level . . . without a tree, shrub, or any other herbage to intercept the vision . . . the almost total absence of water causes all animals to shun it: even the Indians do not venture to cross it except at two or three places." The total picture of the Llano Estacado is one of physical isolation. It is cut off from the rest of the High Plains by the Canadian River, from the more humid lower plains of the east by the Caprock escarpment, and from arid southwestern New Mexico by the Mescalero Escarpment. It merges directly only with the Edwards Plateau to the south.
The underlying rocks of the Llano Estacado consist of clearly defined geologic deposits, which date from near the end of the Paleozoic era. By the end of the late Mesozoic the last retreat of the seas and the building of the Rocky Mountains began. It was the uplift of the Rockies during the Cenozoic (which began 70,000,000 years ago) that provided the materials underlying the Llano Estacado. As rain and snow melt eroded the Rocky Mountains, debris was carried eastward onto the High Plains. As the mountain streams left the precipitous and confining canyons of the high mountains and moved out on the plains, they slowed, and unable to carry the vast load of boulders, pebbles, and silt, dropped those materials into their beds. The stream beds were aggraded, and the streams overflowed and found new avenues of descent over ever lower and flatter terrain. This process left large interconnected alluvial fans much like the deltas which form at some river mouths. The land surface was made up of aggraded materials, which theoretically stretched all the way to the Gulf of Mexico. Calcium carbonate, which had been carried in solution from the mountains, seeped into the alluvial deposits and through evaporation formed a hard caprock of impervious material, commonly called caliche. Subsequent fracturing of the caliche caprock allowed weathering by wind and water of the more humid east to form the lower plains of Texas but left the more arid Llano Estacado high and dry.
All streams flowing east from the Llano Estacado have their origin on the caprock and flow out onto the lower plains through the Caprock escarpment. That drainage flows eastward out of Palo Duro Canyon and Tule Canyon. Both are tributaries of the Prairie Dog Town Fork of the Red River. Running Water Creek, the Double Mountain Fork, and Yellow House Creek are tributaries of the Brazos River. Sulfur Springs Creek, McKenzie Draw, Seminole Draw, Mustang Creek, Monument Draw, and Johnson Draw are all tributary to the Colorado River. Formations on the east, north, and western boundaries of the Llano Estacado probably account for its name. These steep escarpments of fifty to 300 feet were caused by the slumping of the less resistant beds that underlie the hard, resistant Caprock. To Europeans who approached the High Plains from the west, across the Pecos, the sheer cliffs of the Mescalero Escarpment near the site of present Cuero, New Mexico, appeared to be stockaded or palisaded like a fort. The precipitous bluffs formed by erosion of the caprock and the resultant slumping were described by Coronado and other early European explorers as "palisades, ramparts, or stockades." Later, Thomas Falconer, in Letters and Notes on the Santa Fe Expedition (1844), described the escarpment as "elevated or palisaded much as palisaded sides of a fort." References to other "stakes" abound. All are associated with finding one's way to water or marking a route on the treeless and featureless high plain. Early travelers used stakes to mark routes, cowboys to tether horses, or Indians to torture enemies. In the sources, however, stakes are either not defined at all or are variously described-on the Coronado expedition as "piles of bones and cow dung," for instance. Marcy, in his Exploration of the Red River (1849), mentions piles of "stones and buffalo dung." J. Evetts Haley in Charles Goodnight, Cowboy and Plainsman (1936), tells of finding "mojoneras [landmarks] of stone" marking waterholes. Though these references to the use of markers provide a plausible theory for the origin of the name, the express metaphoric comparison of cliff formations and palisades made repeatedly by explorers argues more convincingly for the geological origin.
A critical shortage of water restricted the early exploration and settlement of the Llano Estacado, which is at best a semiarid region with a very high evaporation rate. The rate of precipitation decreases from twenty-two or twenty-three inches annually in the east to only fourteen or fifteen inches in the west. The gently sloping surface directs most of the sparse rainfall into numerous shallow depressions, where the impervious Caprock inhibits its percolation to the underground. The runoff evaporates. Minerals left behind by the process render most surface water in playas unusable. The only reliable source of groundwater has been the Ogalalla Aquifer. This huge underground reservoir extends all along the North American High Plains east of the Rocky Mountains. Its southern extension under the Llano Estacado has been cut off and sealed mainly by the drainage of the Pecos River and, to a lesser extent, by the Canadian River and their tributaries. That isolation prevents any recharge from Rocky Mountain runoff, making the groundwater under the Llano Estacado a finite resource that is being rapidly depleted.
Development of the Llano Estacado did not begin until the 1870s. By the end of 1886 the area and adjacent lands had at least thirty large ranches recognized by name and cattle brand, grazing thousands of cattle on free grass and water on mostly unappropriated public lands. Some of the larger ranches were the Quarter Circle T, JA, Rocking Chair, LX, Turkey Track, T Anchor, Shoe Bar, Frying Pan, and Matador. Most of the largest ranches were broken up by 1920, and much of the land came under the control of land developers and speculators who promoted active and successful campaigns to bring new settlers to West Texas. Innovative farmers learned techniques to make the rich, dry land productive; they also drilled into the Ogalalla Aquifer. Development of animal, windmill, and engine-powered pumps led to massive irrigation programs. Cotton, corn, wheat, sorghum, and a great variety of melons and vegetables are now grown on the Llano Estacado. Natural gas was discovered in Potter County in 1917 and oil in Carson County in 1921. These initial discoveries led to the development of the vast West Texas oilfields, which by 1981 had yielded a total of 46,691,878,324 barrels of crude oil. The discovery and development of the oil and gas fields brought large-scale industry to the Llano area in the 1930s. Thus within a relatively short period the Llano witnessed the most rapid development of any section of the state, progressing from an economy based on unfenced public grazing land to a modern industrial economy within half a century. The earliest ranches on the Llano Estacado were supported by the pioneer settlements of Tascosa, Mobeetie, and Clarendon. The total population of the Llano in 1880 was only 1,081. By 1980 the total was over 900,000 with approximately 23 percent living in rural areas and 77 percent in urban centers. In 1990 there were four metropolitan statistical areas on the plateau, Amarillo, Lubbock, Midland, and Odessa.