Plains Indian (also called North American Plains or Buffalo Indian) is any member of various tribes of American Indians that formerly inhabited the Great Plains of what is now the central United States and south-central Canada, between the Mississippi River and the Rocky Mountains.

The Plains Indians included groups speaking Algonquian, Siouan, Caddoan, Uto-Aztecan, Athabascan, and Kiowa-Tanoan languages.

Most of the Plains Indians were nomadic big-game hunters, and their primary game was the American bison, or buffalo, which supplied them with food, shelter, clothing, and bone tools. Other game included antelope, deer, and elk. Hunting, usually a tribal activity, involved driving the game down a cliff or into a corral or encircling it by fire.

Until the late 16th century the Great Plains were occupied only sparsely or intermittently. Toward the year 1600, however, Spanish horses were introduced and spread northward from the region of New Mexico, reaching almost the entire Plains area by 1750.

Horses and firearms revolutionized the buffalo hunt. The horse made it possible to approach the herd quickly and without disguises. It also seems to have drawn peoples from surrounding areas into the plains to develop a new way of life. Thus, most tribes thought by Europeans to be typical nomadic horse Indians--such as the Cheyenne, Arapaho, and Dakota (Sioux)--were actually newcomers to the area and had been farmers and village dwellers not many generations before their first European contacts.

The nomadic tribes were made up of smaller local units called bands, which came together only for the summer communal hunt or for major religious ceremonies. The Teton Sioux, Cheyenne, Comanche, and Crow were typical nomadic tribes. A few tribes, though mainly nomadic, practiced horticulture, produced pottery, and resided in fixed villages for part of the year. These semisedentary tribes spent part of the time planting and harvesting crops, which consisted of corn (maize), beans, squash, and sunflowers. The Pawnee, Mandan, Hidatsa, and Arikara were typical semisedentary tribes.

There were no hereditary social classes among the Plains Indians, although wealth and standing could be won through prowess at war, generosity to the poor, sharing goods with relatives, and lavish hospitality. Because individualism and fighting were highly valued by almost every tribe, military organizations and clubs were often established in order to channel intratribal aggressiveness.

Local bands and villages were composed of families and kinship groups, which could be patrilineal (as among the Iowa, Kansa, Omaha, Osage, and Ponca), matrilineal (as among the Hidatsa, Mandan, and Crow), or both. Marriages were generally monogamous and were ordinarily arranged between the families of the bride and groom. Children were trained for adult pursuits as part of their play, and relatives often played important roles in their upbringing. Boys were given bows and arrows at a very early age, while girls were taught domestic skills by their mothers.

Before the appearance of European explorers, the Plains Indians made tools of bone, horn, antler, and stone. Animal skins were used for clothing, receptacles of various kinds, and tepees, which were portable, cone-shaped tents. Basketry and pottery were known among the semisedentary tribes. Until horses were introduced by the Spaniards, dogs were probably the only domesticated animals. The introduction of the horse had a profound impact on Plains life, revolutionizing the hunt and warfare and providing a valuable commodity for both trade and theft, the latter stimulating warfare.

Although some tribes, such as the Atsina*, believed in a supreme deity, other tribes, such as the Crow, did not. However, rituals ranging from simple rites to ceremonies lasting weeks were common to almost all of the Plains Indians. All of the Plains tribes had medicine men, or shamans, who were responsible for such activities as curing illness and locating enemies, game, or lost objects. Much importance was attached to spiritual visions, and success in life was attributed to the intervention of friendly spirits.

The culture of the Plains Indians changed radically as white settlers moved into the region. The nomadic Indians' hunting economy collapsed when the buffalo was virtually exterminated in the late 19th century, and native crafts declined as manufactured articles, such as metal utensils and cloth, were introduced. Introduced diseases and warfare with whites reduced Indian populations, and even greater disturbances resulted when the Indians were placed on reservations. Nomadic Indians found cattle a poor replacement for buffalo, and semisedentary groups, who considered cultivation to be women's work, resisted the change in the division of labour brought on by the introduction of the plow. Deprived of their traditional culture, many Indians became demoralized and came to depend on government aid for their subsistence.

**Atsina: also called Gros Ventres Of The Prairie, an offshoot of the Algonquian-speaking Arapaho tribe of North American Indians, from which they may have separated as early as 1700; they were living in what is now northern Montana and adjacent regions of Canada in late historic times and were culturally similar to other Plains tribes. Together with the Assiniboin, they were settled on Fort Belknap Reservation, Montana, where the combined population totalled fewer than 2,000 in the late 20th century.