Sand Creek was one of many assaults on American Indians during the war, from Patrick Edward Connor’s massacre of Shoshone villagers along the Idaho-Utah border at Bear River on Jan. 29, 1863, to the forced removal and incarceration of thousands of Navajo people in 1864 known as the Long Walk.

In terms of sheer horror, few events matched Sand Creek. Pregnant women were murdered and scalped, genitalia were paraded as trophies, and scores of wanton acts of violence characterize the accounts of the few Army officers who dared to report them. Among them was Capt. Silas Soule, who had been with Black Kettle and Cheyenne leaders at the September peace negotiations with Gov. John Evans of Colorado, the region’s superintendent of Indians affairs (as well as a founder of both the University of Denver and Northwestern University). Soule publicly exposed Chivington’s actions and, in retribution, was later murdered in Denver.

After news of the massacre spread, Evans and Chivington were forced to resign from their appointments. But neither faced criminal charges, and the government refused to compensate the victims or their families in any way. Indeed, Sand Creek was just one part of a campaign to take the Cheyenne’s once vast land holdings across the region. A territory that had hardly any white communities in 1850 had, by 1870, lost many Indians, who were pushed violently off the Great Plains by white settlers and the federal government.