 The Indians' response to the Sand Creek Massacre was a move northward to the more isolated lands of Wyoming to join their relatives, the Northern Cheyenne, the Northern Arapaho, and the main body of the Sioux.En route they carried out extensive raids along the South Platte River and attacked U.S. military forts and forces, successfully eluding defeat and capture by the U.S. army.By the terms of the 1851 Treaty of Fort Laramie between the United States and various tribes including the Cheyenne and Arapaho, the United States unilaterally defined and recognized Cheyenne and Arapaho territory as ranging from the North Platte River in present-day Wyoming and Nebraska southward to the Arkansas River in present day Colorado and Kansas.