Which 1864 Colorado event became one of the most notorious attacks on Cheyenne and Arapaho people?

The Sand Creek massacre was the 1864 Colorado attack on a Cheyenne and Arapaho encampment.

On November 29, 1864, Colorado Territory militia commanded by Colonel John Chivington attacked a village led by Cheyenne chief Black Kettle and Arapaho leaders. The camp was near Sand Creek in southeastern Colorado, and many residents believed they were under U.S. protection.

Most of those killed were women, children, and elderly people. Estimates vary, but historians commonly place the number of Native victims in the range of roughly 150 to 200. The attack provoked widespread condemnation, including testimony from U.S. officials and soldiers.

The event intensified conflict on the Great Plains and damaged Black Kettle’s efforts to pursue peace. It is also frequently confused with the 1868 Battle of the Washita, another U.S. attack on a Southern Cheyenne village.