On November 29, 1864, Colonel John M. Chivington led approximately 700 U.S. volunteer soldiers to a village of about 500 Cheyenne and Arapaho people camped along the banks of Big Sandy Creek in southeastern Colorado. Although the Cheyenne and Arapaho people believed they were under the protection of the U.S. Army, Chivington's troops attacked and killed about 150 people, mainly women, children, and the elderly. Ultimately, the massacre was condemmed following three federal investigations.

The Sand Creek Massacre National Historic Site was authorized by Public Law 106-465 on November 7, 2000. The purposes of the Act are to recognize the national significance of the massacre in American history, and its ongoing signficance to the Cheyenne and Arapaho people and descendents of the massacre victims. The Act authorizes establishment of the national historic site once the NPS has acquired sufficient land from willing sellers to preserve, commemorate, and interpret the massacre. Acquisition of a sufficient amount of land has not yet occured. Currently, the majority of land within the authorized boundary is privately owned and is not open to the public. The NPS is working in partnership with The Conservation Fund, the Cheyenne and Arapaho Tribes, and the State of Colorado towards establishment of the Sand Creek Massacre National Historic Site.