The Dakota War of 1862, also known as the Sioux Uprising, the Dakota Uprising, the Sioux Outbreak of 1862, the Dakota Conflict, the U.S.-Dakota War of 1862, or Little Crow's War, was an armed conflict between the United States and several bands of eastern Dakota also known as the Santee Sioux. It began on August 18, 1862, at the Lower Sioux Agency along the Minnesota River in southwest Minnesota.The eastern Dakota were pressured into ceding large tracts of land to the United States in a series of treaties signed in 1837, 1851 and 1858, in exchange for cash annuities, debt payments, and other provisions.:2 All four bands of eastern Dakota, particularly the Mdewakanton, were displaced and reluctantly moved to a reservation that was twenty miles wide, ten on both sides of the Minnesota River.:23 There, they were encouraged by U.S. Indian agents to become farmers rather than continue their hunting traditions.:45 Meanwhile, the settler population in Minnesota Territory had grown from 6,077 in 1850 to 172,072 in 1860, after it had become a state. A crop failure in 1861, followed by a harsh winter along with poor hunting due to depletion of wild game, led to starvation and severe hardship for many of the eastern Dakota. In the summer of 1862, tensions between the eastern Dakota, the traders, and the Indian agents reached a breaking point, because the Indian agents were late with the U.S. government annuity payments owed to the eastern Dakota. The traders refused to extend credit to the tribesmen for food, in part because the traders suspected the payments might not arrive at all due to the American Civil War.:116,121On August 17, 1862, four young native men killed five white settlers in Acton, Minnesota. That night, a faction led by Chief Little Crow decided to attack the Lower Sioux Agency the next morning in an effort to drive all settlers out of the Minnesota River valley.:12 In the weeks that followed, Dakota warriors attacked and killed hundreds of settlers, causing thousands to flee the area,:107and took hundreds of "mixed-blood" and white hostages, almost all women and children. The demands of the Civil War slowed the U.S. government response, but on September 23, 1862, an army of volunteer infantry, artillery and citizen militia assembled by Governor Alexander Ramsey and led by Colonel Henry Hastings Sibley finally defeated Little Crow at the Battle of Wood Lake.:63By the end of the war, 358 settlers had been killed, in addition to 77 soldiers and 29 volunteer militia. The total number of Dakota casualties is unknown. On September 26, 1862, 269 "mixed-blood" and white hostages were released to Sibley's troops at Camp Release. Approximately 2,000 Dakota surrendered or were taken into custody, including at least 1,658 non-combatants, as well as those who had opposed the war and helped to free the hostages.:233 Meanwhile, Little Crow and a group of 150 to 250 followers fled to the northern plains of Dakota Territory and Canada.:83 In less than six weeks, a military commission, composed of officers from the Minnesota volunteer Infantry, sentenced 303 Dakota men to death. President Abraham Lincoln reviewed the convictions and approved death sentences for 39 out of the 303.:72 On December 26, 1862, 38 were hanged in Mankato, Minnesota with one getting a reprieve. This was the largest one-day mass execution in American history. The United States Congress abolished the eastern Dakota and Ho-Chunk (Winnebago) reservations in Minnesota and declared their treaties null and void. In May 1863, the eastern Dakota and Ho-chunk imprisoned at Fort Snelling were exiled from Minnesota. They were placed on riverboats and sent to a reservation in present-day South Dakota. The Ho-Chunk were also initially forced to the Crow Creek reservation, but would later move to Nebraska near the Omaha people to form the Winnebago Reservation.:76,7980In 2021, the Minnesota state legislature and the Minnesota Historical Society (MNHS) transferred ownership of 115 acres of land back to the Lower Sioux Indian Community (LSIC), including about half of the lands near the Lower Sioux Agency and part of the historic site of battle. The MNHS and the LSIC have been jointly administering the site.

The American Indian Wars, also known as the American Frontier Wars, the First Nations Wars in Canada (French: Guerres des Premières Nations), and the Indian Wars, were fought by European governments and colonists in North America, and later by the United States and Canadian governments and American and Canadian settlers, against various American Indian and First Nation tribes. These conflicts occurred in North America from the time of the earliest colonial settlements in the 17th century until the early 20th century. The various wars resulted from a wide variety of factors. The European powers and their colonies also enlisted allied Indian tribes to help them conduct warfare against each other's colonial settlements. After the American Revolution, many conflicts were local to specific states or regions and frequently involved disputes over land use; some entailed cycles of violent reprisal.

As settlers spread westward across North America after 1780, armed conflicts increased in size, duration, and intensity between settlers and various Indian and First Nation tribes. The climax came in the War of 1812, when major Indian coalitions in the Midwest and the South fought against the United States and lost. Conflict with settlers became much less common and was usually resolved by treaty, often through sale or exchange of territory between the federal government and specific tribes. The Indian Removal Act of 1830 authorized the American government to enforce Indian removal from east of the Mississippi River to Indian Territory west on the American frontier, especially what became Oklahoma. The federal policy of removal was eventually refined in the West, as American settlers kept expanding their territories, to relocate Indian tribes to reservations.