The time of the advent of the various tribes of this region is not known, but the semi-sedentary Caddoan peoples—the Pawnee of Nebraska, the Wichita of Kansas and other Caddoan tribes of Arkansas, Oklahoma and Texas—occupied their historically known seats from much earlier times. While Apache bands were met on the western Texas plains when the Spaniards first explored the country in the i6th century, they probably did not pass west ward into New Mexico and Arizona until later ; and the Comanche did not appear in the southern plains until the beginning of the 18th century. The only houses of the entire region that ap proached permanency were the earth-lodges, 3o to 6o feet in diameter, of the Pawnee and Omaha of Nebraska, the Ponca of Nebraska and South Dakota, the Osage of Missouri-Arkansas, and the Arikara, Mandan and Hidatsa of the upper Missouri river in North Dakota. Remains of these are still traceable at old undisturbed village-sites, in the form of rings, for the floor of the earth-lodge was sunk two to four feet below the sur face.
Quarries of flint with associated sites of manufacture of chipped implements are found in Oklahoma, Kansas and Texas, and of quartzite and soapstone in Wyoming, the diggings for the quartz ite being very extensive. Two remarkable deposits, or caches, of flint implements have been found within the region, one con sisting of a thousand specimens in a sulphur spring at Afton, Oklahoma, the other a cache of thousands of flint arrow-points in Delaware county of the same state. Obsidian, a favoured mate rial for projectile points and knives, is abundant in Yellowstone Park and the upper valleys of Snake river, Wyoming and was not only used locally, but found its way by channels of aboriginal barter hundreds of miles from its place of origin. The stone imple ments of the general Plains region reflect the hunting tendencies of the Indians that inhabited it—arrow- and spear-points, knives, scrapers, hammers, club-heads. The heavy grooved hammer used in early as well as in historic times for cracking the bones of the larger mammals for extracting the marrow, for driving stakes, and for pounding seeds, etc., is regarded as probably the most typical and characteristic of the stone tools of this culture area. The hafted stone hammer, used as a club, is thought to have been of somewhat recent introduction. The metate and mano, used for grinding corn by the agricultural Pueblos of the arid region, found their way to a slight extent into the mountains and plains to the north and east, and other evidences of a lowly Pueblo cul ture have been traced to western Texas. In the upper Missouri valley have been found indications of an overflow of such stone objects as tubular tobacco pipes and paddle-shaped clubs, more characteristic of the middle Pacific slope region of Oregon and Washington. In the great central reaches of the area are found
circles and lines of boulders, with an occasional effigy in outline. The so-called "Medicine Wheel" in the Big Horn mountains of Wyoming, with a circumference of 245 feet, is notable. Some of the lines of stones doubtless mark the sites of buffalo pounds, while the small circles may indicate the sites of tipis. Pictographs are not uncommon. Pottery is rare throughout the area, excepting in its eastern fringe, where the western limits of mound-building Indians were reached.
Perhaps no more ancient remains have been found in the area than those recovered from certain dry rock-shelters in the Ozark mountains of western Missouri-Arkansas, which were conducive to the preservation of practically everything their inhabitants used —basketry, cradle-boards of cane, woven bags, fish-nets, over shoes and sandals of grass, moccasins of deerskin, feather robes, pendants and beads of shell, and stone spears which were hurled with an atlatl, or throwing-stick, for they hunted buffalo, elk, deer and turkey. These Bluff-dwellers were agriculturists as well as hunters, raising corn, beans and squashes, and using also for food many wild vegetable products. Little pottery was used. Adja cent caves revealed a later but still prehistoric culture, shown by the presence of the bow instead of the atlatl, and of a superior class of pottery, which may be attributable to the ancestors of the Osage or the Kansa.
In the southernmost part of the Plains area, in Texas, little in tensive research has been conducted. Throughout the limestone region are found numerous and extensive kitchen-middens which give evidence of a hunter culture only ; but along the streams of the central part of the state are many old camp-sites which reveal evidences of a superior culture. In the timber region of eastern Texas are evidences of an early mound-builder culture and of the relatively settled village culture of the historic period; and in the trans-Pecos and Panhandle regions a low form of Pueblo culture has been revealed, with some evidence of Basket-maker life.
VI. The Arid Region.—This area may be said to comprise the present Arizona, New Mexico, Nevada, southern Colorado and Utah, a part of western Texas, and northern Chihuahua. It is largely a region of desert plains, plateaux, canons, mesas and lofty forested mountains, with here and there perennially or inter mittently watered valleys of remarkable fertility when brought under irrigation. In its physiographic features as a whole the territory is quite unlike any other in North America, and therefore the culture of its ancient inhabitants stands alone.