The Dakota War of 1862, also known as the Sioux Uprising, was an armed conflict between the United States and several bands of the Eastern Sioux (also known as eastern Dakota). It began on August 17, 1862, along the Minnesota River in southwest Minnesota. It ended with a mass execution of 38 Dakota men on December 26, 1862, in Mankato, Minnesota.
Throughout the 1850's numerous treaty violations by the United States and late or unfair payments by Indian agents caused increasing hunger and hardship among the Dakota. In 1851 the Treaty of Mendota forced the Dakota to cede large tracts of land in Minnesota Territory to the U.S. In exchange for money and goods, the Dakota were forced to agree to live on a 20 mile wide Indian reservation centered on a 150 mile stretch of the upper Minnesota River. However the United States Senate deleted Article 3 of each treaty, which set out reservations and much of the promised compensation never arrived. Traders with the Dakota had demanded that the government give the annuity payments directly to them, introducing the possibility of unfair dealings between the Indian agents and the traders.
In May of 1858, several Dakota traveled to Washington DC to negotiate enforcing existing treaties. As a result of this, the northern half of the reservation along the Minnesota River was lost, the land divided into townships and plots for settlement. Hunting by settlers dramatically reduced wild game, reducing the meat available for the Dakota, but also reduced their ability to sell furs to traders.
In mid 1862, the Dakota demanded the annuities directly from their agent, Thomas J. Galbraith. The traders refused to provide any more supplies on credit under those conditions and negotiations reached an impasse.
On August 15, 1862, bands met at the Upper Sioux Agency and were rejected for supplies, as the Indian Agent Thomas Galbraith would not distribute food to these bands without payment.
On August 17, 1862, one young Dakota, with a hunting party of three killed five settlers while on a hunting expedition. That night a council of Dakota decided to attack settlements through the Minnesota River valley to try and drive whites out of the area. There has never been an official report on the number of settlers killed, although figures as high as 800 have been mentioned.
Over the next several months, battles continued pitting settlers against the Dakota, and later with the United States Army. It ended with the surrender of most of the Dakota bands. By late December 1862, soldiers had taken captive more than a thousand Dakota who were interned in various jails in Minnesota. After trials and sentencing 38 Dakota were hanged on December 26, 1862, the largest one-day execution in American history. The mass execution was performed publicly on a single scaffold platform. They were buried en masse in a trench in the sane of the riverbank. In April 1863 the rest of the Dakota were expelled from Minnesota to Nebraska and South Dakota, while the United States Congress abolished their reservations.