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 69 to over 600 Native American people. Wikipedia