On November 29, 1864, Cheyenne Chief White Antelope sang his death song as some 200 Arapaho and Cheyenne were massacred by Colorado Volunteers of the U.S. Army at Sand Creek in southeastern Colorado Territory. The Indians had been promised safety by the military and some even gathered futilely under the Stars and Stripes hoisted at the encampment above a white flag of peace.

In a bitterly cold dawn, about 700 members of the Third Regiment of Colorado Volunteers rode through the camp in a sneak attack, shooting mostly women, children and elderly in an hours-long frenzy. Many of the victims’ bodies were mutilated by soldiers—some of them said to be drunk—and disfigured remains were paraded through the streets of Denver to jubilation and applause.

In the months immediately before the massacre, freight from the east to Denver was largely at a standstill as Indians disrupted travel in an attempt to ward off further intrusion. Flour was $45 a sack and other prices skyrocketed, adding to the hysteria fanned by Indian-war proponents. Another impetus to violence, the scalped remains of a family of four from near Denver were brought to the city for display, although whether they were killed by Indians has been disputed.

Before Sand Creek, the Cheyenne were still recovering from an 1849 cholera epidemic that killed nearly half the tribe, and they were receiving conflicting signals from the U.S. Army. Although Army Col. John Chivington and Territorial Gov. John Evans did not accept Indians’ commitments to peace, Cheyenne Chief Black Kettle nevertheless agreed to a camp at Sand Creek believing he had a promise of safety from Army Major Edward Wynkoop.

The seeds of conflict first emerged in the invasion of the tribes’ ancestral homelands by increasing numbers of white settlers and the hordes of the western gold rush. Although the Fort Laramie Treaty of 1851 promised vast lands to the Arapaho and Cheyenne to discourage warfare, the pressure of white encroachment resulted in a new treaty and tribal anger about the much smaller reservation that resulted. Added to that and other grievances, Chivington, a Methodist minister who later commanded the soldiers at Sand Creek, recognized violence against Indians as a way to enhance the political clout he hoped would make him a delegate to the U.S. Congress after Colorado Territory achieved statehood—which, ironically, was delayed 12 years, partly because of national horror at the massacre.

To further his political ends, Chivington’s troops became the “Bloody Thirdsters” instead of the “Bloodless Third” as they had earlier been termed publicly because the 100-day enlistees had not seen combat before Sand Creek.

The legacy of the murder at Sand Creek included angry retaliation by survivors immediately and into the future, including in the Battle of the Little Bighorn 12 years later. After the massacre, young men of the Cheyenne, Arapaho and Sioux gathered in the northeast corner of Colorado Territory where they killed travelers in wagon trains and soldiers from a nearby fort and devastated Julesburg twice. But over the long term, the deaths of chiefs and headmen at Sand Creek damaged the social structure of the tribes, disrupting tribal societies and leadership through the years.

Chivington gave testimony to Congress about the massacre, but he could not be court-martialed because he had been relieved of his command after the Sand Creek tragedy and was discharged from military service.