The Sand Creek Massacre was a massacre of Cheyenne and Arapaho people by the U.S. Army in November 1864. It is considered to be one of the most horrific massacres in American history. The massacre was ordered by Colonel John Chivington, who led a force of over 700 troops against a peaceful Cheyenne and Arapaho village on Sand Creek in what is now Colorado. The soldiers killed over 150 people, including women, children, and infants. The massacre was a clear violation of the peace treaty that had been signed between the U.S. government and the Cheyenne and Arapaho people just a few months earlier.
The Sand Creek Massacre is often cited as an example of how the peace between the U.S. government and Native American tribes was broken. The massacre led to decades of conflict between the U.S. military and Native American tribes in the West.