The Lakota are closely related to the western Dakota of Minnesota. After their adoption of the horse in the early 18th century, the Lakota became part of the Great Plains culture with their eventual Algonkin-speaking allies, the Tsitsistas (Cheyenne), living in the northern Great Plains. Their society centered on the buffalo hunt with the horse. There were 20,000 Lakota in the mid-18th century. The number has now increased to about 70,000, of whom about 20,500 still speak their ancestral language. After 1720, the Lakota branch of the Seven Council Fires split into two elements, the Saone who moved to the Lake Traverse area on the South Dakota-North Dakota-Minnesota border, and the Oglala-Brulé who occupied the James River Valley. By about 1750, however, the Saone had moved to the east bank of the Missouri, followed 10 years later by the Oglala and Brulé (Sicangu).

The large and powerful Arikara, Mandan, and Hidatsa villages had prevented the Lakota from crossing the Missouri for an extended period, but when smallpox and other diseases nearly destroyed these tribes, the way was open for the first Lakota to cross the Missouri into the drier, short-grass prairies of the High Plains. These Saone, well-mounted and increasingly confident, spread out quickly. In 1765, an Saone exploring and raiding party led by Chief Standing Bear discovered the Black Hills (which they called the Paha Sapa). Just a decade later, in 1775, the Oglala and Brulé also crossed the river, following the great smallpox epidemic of 1772-1780, which destroyed 3/4 of the population of the Missouri Valley populations. In 1776, they defeated the Cheyenne as the Cheyenne had earlier defeated the Kiowa, and gained control of the land which became the center of the Lakota universe.

Initial contacts between the Lakota and the United States, during the Lewis and Clark Expedition of 1804-06, were friendly. But as more and more settlers crossed Lakota lands, this changed. In Nebraska on September 3, 1855, 700 soldiers under American General William S. Harney avenged the Grattan Massacre by attacking a Lakota village, killing 100 men, women, and children. Other wars followed; and in 1862-1864, as refugees from the "Sioux Uprising" in Minnesota fled west to their allies in Montana and Dakota Territory, the war followed them.Because the Black Hills are sacred to the Lakota, they objected to mining in the area, which has been attempted since the early years of the 19th century. In 1868, the US government signed the Fort Laramie Treaty (1868) with them exempting the Black Hills from all white settlement forever. Four years later, gold was publicly discovered there, and an influx of prospectors descended upon the area, abetted by army commanders like General George Armstrong Custer. The latter tried to administer a lesson of noninterference with white policies, resulting in the Black Hills War of 1876-77.The Lakota with their allies, the Arapaho and the Cheyenne, defeated the U.S. 7th Cavalry in 1876 at the Battle at the Greasy Grass or Little Big Horn, killing 258 soldiers and inflicting more than 50% casualties on the regiment. But like the Zulu triumph over the British at Isandlwana in Africa three years later, it proved to be a pyrrhic victory. The Teton were defeated in a series of subsequent battles by the reinforced U.S. Army, and were herded back onto reservations, by preventing buffalo hunts and enforcing government food distribution policies to 'friendlies' only. The Lakota were compelled to sign a treaty in 1877 ceding the Black Hills to the United States, but a low-intensity war continued, culminating, fourteen years later, in the killing of Sitting Bull (December 15, 1890) at Standing Rock and the Massacre of Wounded Knee (December 29, 1890) at Pine Ridge.

Today, the Lakota are found mostly in the five reservations of western South Dakota: Rosebud (home of the Upper Sicangu or Brulé), Pine Ridge (home of the Oglala), Lower Brulé (home of the Lower Sicangu), Cheyenne River (home of several other of the seven Lakota bands, including the Sihasapa and Hunkpapa), and Standing Rock, also home to people from many bands. But Lakota are also found far to the north in the Fort Peck Reservation of Montana, the Fort Berthold Reservation of northwestern North Dakota, and several small reserves in Saskatchewan and Manitoba, where their ancestors fled to "Grandmother's Land" (Canada) during the Minnesota or Black Hills War. Large numbers of Lakota also live in Rapid City and other towns in the Black Hills, and in Metro Denver.

Information excerpt from:Wikipedia