There were three main divisions of the Sioux: Santee, Yankton, and Teton, calling themselves, respectively, Dakota, Nakota, and Lakota. The Santee, or Eastern Sioux, comprised the Mdewkanton, Wahpeton, Wahpekute, and Sisseton; the Yankton included the Yankton and Yanktonai; and the Teton, or Western Sioux, had seven main divisions--the Sihasapa, or Blackfoot; Brulé (Upper and Lower); Hunkpapa; Miniconjou; Oglala; Sans Arcs; and Oohenonpa, or Two-Kettle.

Further Divisions included: Dhegiha, Chiwere, Mandan, and Hidatsa. (see table above)

Before the middle of the 17th century, the Santee Sioux lived in the area around Lake Superior, where they gathered wild rice and beans, hunted deer and buffalo, and speared fish from canoes. Prolonged and continual warfare with the Ojibwa drove the Santee into southern and western Minnesota; the Teton and Yankton divisions were forced permanently from Minnesota onto the Great Plains (in present North and South Dakota), where they ceased to carry on their traditional agricultural activity and adopted the Plains way of life, which centred on the nomadic hunting of buffalo and other big game.

The Sioux shared many cultural characteristics with other Plains Indian societies. They lived in tepees (a Sioux word). Men acquired status by performing brave deeds in warfare; horses and scalps obtained in a raid were evidence of valour. Warfare and supernaturalism were closely connected, to the extent that designs suggested in mystical visions were painted on war shields to protect the bearers from their enemies. The Sioux practiced an elaborate form of the sun dance, their chief tribal festival. Their religious system recognized four powers as presiding over the universe, and each power in turn was divided into hierarchies of four. The buffalo figure also had a prominent place in their religion. Among the Teton Sioux the bear was important; bear power obtained in a vision was regarded as curative. The Santee Sioux engaged in a ceremonial bear hunt to protect their warriors before their departure on a raid.

Sioux women were skilled at porcupine-quill and bead embroidery bearing geometric designs. Police functions were performed by military societies, the most significant duty of which was overseeing the buffalo hunts. Other societies included dance, shamanistic, and women's societies.

Of all the Plains tribes, the Sioux were the most resolute in resisting white men's incursions upon their land. With the advance of the white frontier west of the Mississippi River in the mid-19th century, the United States sought to forestall Indian trouble by negotiating the First Treaty of Fort Laramie (1851) with the Sioux, Shoshoni, Cheyenne, Arapaho, and other Western tribes. The treaty assigned boundaries to each tribe throughout the northern Great Plains and arranged for forts and roads within Indian territory.

In 1851 and 1859 the Santee Sioux gave up most of their land in Minnesota and were assigned a reservation on which they were encouraged to practice settled agriculture. White violations of the treaties, however, together with the pressure of the advancing white frontier, led the Santee Sioux to mount a bloody uprising in 1862 under the leadership of Little Crow. After their defeat, the Santee Sioux were forced to move westward to reservations in Dakota and Nebraska.

The territory of the nomadic Teton and Yankton Sioux, which included the area between the Missouri River and the Teton Mountains and between the Platte River on the south and the Yellowstone River on the north, was invaded increasingly by whites after the Gold Rush of 1849. These Sioux tribes were particularly incensed by the government's attempt to build a road to Bozeman, Mont. (the Powder River Road), across their favourite hunting grounds in the Bighorn Mountains. In 1865-67 Red Cloud, an Oglala chief, led thousands of Sioux warriors in a campaign to halt the road's construction.

On Dec. 21, 1866, a band under Chief High Backbone was responsible for the Fetterman Massacre, a battle in which more than 80 U.S. soldiers were trapped and killed near Fort Phil Kearny. The United States eventually acknowledged defeat in the Second Treaty of Fort Laramie (1868), in which the government agreed to abandon the Bozeman Trail and guaranteed the Sioux exclusive possession of the area in South Dakota west of the Missouri River.

When gold was discovered in the Black Hills of South Dakota in the mid-1870s, however, thousands of miners chose to disregard the Second Treaty of Fort Laramie and swarmed onto the Sioux reservation, thus precipitating another round of hostilities in 1876. At the Battle of the Little Bighorn in June 1876, a large contingent of Sioux and Cheyenne were able to overwhelm Lieutenant Colonel George A. Custer and wipe out his entire band of more than 200 men, but this spectacular Indian victory did not affect the course of the larger war.

Later that summer 3,000 Sioux were trapped at the Tongue River valley by the main army of General Alfred H. Terry, and the Sioux surrendered on October 31, after which the majority returned to their reservations. The chiefs Sitting Bull, Crazy Horse, and Gall refused, however, to take their bands into the reservations. Crazy Horse was killed following his surrender in 1877, while Sitting Bull escaped to Canada, returning to the United States in 1881. In 1890-91 the Ghost Dance religion, which preached the coming of a messiah, a return to the old nomadic hunting life, and reunion with the dead, began to take a strong hold among the Sioux people, who had suffered harsh privations while confined to their reservations. Believing that the movement was disturbing an uneasy peace, government agents moved to arrest its ringleaders. Sitting Bull was killed in 1890 by Indian police taking him into custody. Finally, the U.S. troops' massacre of many Sioux men, women, and children at Wounded Knee in December 1890 marked the end of all Sioux resistance to white domination. (See Crazy Horse.)

In the late 20th century the Sioux numbered about 40,000; more than 75 percent of them lived on reservations in North and South Dakota, Montana, and Nebraska. A few thousand more lived in Canada.