The 1851 Fort Laramie Treaty recognized a large territory on the central Plains for the Cheyenne and Arapaho. In the following decade, increasing U.S. migration and settlement pressure in Colorado helped set the stage for conflict over land, resources, and authority.
Cheyenne and Arapaho leaders met with Colorado territorial officials and U.S. Army representatives at the Camp Weld Council. Participants discussed how “friendly” bands might avoid attacks, but the meeting did not produce a binding peace treaty and left key authority questions unresolved.
Maj. Edward W. Wynkoop, who had tried to protect and negotiate with Cheyenne and Arapaho groups near Fort Lyon, was relieved and departed the post. Command transferred to Maj. Scott Anthony just days before the attack at Sand Creek, a leadership change that mattered because it affected how Native camps near the fort were treated.
Colorado volunteers under Col. John M. Chivington attacked a Cheyenne and Arapaho encampment along Big Sandy (Sand) Creek in southeastern Colorado Territory. Many victims were women, children, and elderly people; survivors fled north, and the violence reshaped relations between the United States and Plains tribes.
News of the killings spread quickly, and many Cheyenne and Arapaho—joined by some Lakota—moved toward retaliation and war. This escalation is often described as the Colorado War’s intensified phase, as fighting shifted to settlements, routes, and military posts across the region.
A large force of Cheyenne, Arapaho, and Lakota attacked near Julesburg, Colorado, defeating local U.S. forces and then raiding along the South Platte River corridor. The event showed how quickly Sand Creek helped expand conflict from one site into a broader frontier war.
Rumors of atrocities led to formal investigations, including testimony taken in early 1865. Capt. Silas Soule—who kept his men from firing at Sand Creek—testified that women and children were shot and that mutilations occurred, evidence that helped reframe the event as a massacre rather than a battle.
A congressional report published as part of the Joint Committee on the Conduct of the War’s work included testimony on the “massacre of the Cheyenne Indians.” The federal scrutiny damaged reputations and confirmed, in official records, that the attack targeted a camp that included many noncombatants.
Silas Soule was killed in Denver after his public testimony against Chivington and the Sand Creek attack. His death became part of the massacre’s aftermath, illustrating the risks faced by witnesses in a politically charged environment.
U.S. commissioners and Cheyenne and Arapaho leaders signed the Treaty of the Little Arkansas River, which explicitly renounced the Sand Creek attack and promised reparations and other provisions. The treaty aimed to reduce violence and reset relations, even as the broader pattern of forced removals continued.
More than a century later, Congress authorized a national historic site to commemorate Sand Creek and support public education about what happened there. This step marked a shift toward formal national recognition and preservation of the landscape tied to the massacre.
The Sand Creek Massacre National Historic Site was formally opened, creating a dedicated place for remembrance and interpretation. The site’s establishment highlights the lasting legacy of the Colorado War era and the continuing importance of Sand Creek for Cheyenne and Arapaho descendant communities.
Sand Creek Massacre and the Colorado War (1864–1865)