The Sand Creek Massacre occurred on November 29, 1864, when a group of Colorado U.S. Volunteer Cavalry attacked a peaceful camp of the Cheyenne and Arapaho tribes near Sand Creek in Colorado Territory. The camp was led by Chief Black Kettle, who believed they were under U.S. protection. The soldiers killed an estimated 150 Native Americans, mostly women and children, despite the tribe's efforts to signal their peaceful intentions. The massacre was part of the broader conflict between the U.S. government and Native American tribes during westward expansion. It sparked outrage and condemnation, leading to increased tensions and violence in the region. The event remains a significant and tragic chapter in American history, highlighting the struggles faced by Indigenous peoples.