The name “Sioux” originates from a French version of the Ojibway word “Nadouessioux” (meaning “little snakes”), and included “seven council fires” (tribes) in a loosely aligned federation united by a common language and variations of that language.
Originally inhabiting the Great Lakes region, in the 17th century the Sioux tribes were pushed westward into the Great Plains, most likely by the Iroquois (who themselves were likely pushed westward by European settlers).
They adapted quickly to their new environment, becoming nomadic and following the buffalo herds, which became their primary source of food, clothing and shelter (when a buffalo was hunted and killed, virtually nothing went to waste).
After the Louisiana purchase in 1803 (which included the majority of the lands on which the Sioux lived), white migration to the area began in earnest as the new territory became a destination for settlers. Inevitably, encroachment by the settlers conflicted with the lives of the Sioux, as the settlers also hunted buffalo, thinning the herds substantially.
In 1868, the Treaty of Fort Laramie was signed by the US and the Lakota, several other Sioux tribes, and the Arapaho. It created the “great reservation,” guaranteeing ownership of the Black Hills for the Lakota, and further land and hunting rights in South Dakota, Wyoming, and Montana. It also closed the Powder River Country (in northeastern Wyoming) to all whites. This treaty ended Red Cloud's War, which had been ongoing since 1866 over control of the Powder River Country.
After gold was discovered in the Black Hills in 1874, the government tried to convince the Sioux to sell the Black Hills (considered a sacred place to the Sioux, since this is where their creation stories say they emerged onto the Earth's surface).
When the government was unable to acquire the Black Hills, it ordered all Indians living outside the reservations to return to the reservations by January 31, 1876, or be sent back by force. Among those who refused to follow the government order were two groups led by Crazy Horse and Sitting Bull. When George Armstrong Custer and his Seventh Cavalry attacked them on June 25, 1876, he and his entire command were killed at Little Big Horn River in southeastern Montana.
By 1889, a new spiritual movement among the Sioux called the “Ghost Dance” brought renewed hope to the Sioux for taking back their lands. Upset by multiple violations of the Fort Laramie Treaty by the US, and continued encroachment by settlers and railroads on the reservation, as well as the dispute over the Black Hills land, there was substantial unrest among the Sioux.
A series of battles and assaults were made by the US to quell the unrest, the most well-known of them being the Wounded Knee Massacre on December 29, 1890. Purportedly caused by miscommunication, the massacre resulted in 250-300 Lakota deaths, and 51 wounded (nearly half the casualties were women and children). 25 US soldiers also died, and 39 were wounded.
Today the Great Sioux Nation is the third largest of the Native American nations at about 114,000 people. It includes three divisions – the Eastern or Dakota, the Middle or Nakota, and the Western or Lakota.