Sand Creek massacre

The Sand Creek massacre was a massacre of Cheyenne and Arapaho people by the U.S. Army in the American Indian Wars that occurred on November 29, 1864, when a 675-man force of the Third Colorado Cavalry under the command of U.S. Volunteers Colonel John Chivington attacked and destroyed a village of Cheyenne and Arapaho people in southeastern Colorado Territory, killing and mutilating an estimated 70–500 Native Americans, about two-thirds of whom were women and children. The location has been designated the Sand Creek Massacre National Historic Site and is administered by the National Park Service. This was part of a series of events known as the Colorado War and was preceded by the Hungate massacre.
By the terms of the 1851 Treaty of Fort Laramie between the United States and seven Indian nations, including the Cheyenne and Arapaho, the United States recognized that the Cheyenne and Arapaho held a vast territory encompassing the lands between the North Platte River and the Arkansas River, and eastward from the Rocky Mountains to western Kansas. This area included present-day southeastern Wyoming, southwestern Nebraska, most of eastern Colorado, and the westernmost portions of Kansas.

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