The Arapaho, who call themselves 'Inuna-ina', are close allies with the Cheyenne. This name is roughly translated into 'our people'.

The Araphoe were mounted buffalo hunters of the plains but came from what is now northern Minnesota where they were farmers. When they migrated from the east, they split into a northern and southern tribe. The larger body now lives with the Cheyenne in Oklahoma, while the northern division resides with the Shoshone on a reservation in Wyoming. Like the Cheyenne, they spoke an Algonquin language, and they celebrated the Sun Dance, and later the Ghost Dance.

In what became known as the Sand Creek Massacre, at least 150 Arapaho and Cheyenne people were killed, their horses taken, and all their belongings destroyed. During the ensuing conflict on the Plains, the military tended to define unsettled Arapaho bands as "hostile," and were frequently attacked along with the Cheyenne and Lakota Sioux.

Around the time of the Sand Creek Massacre, much of the southern Arapaho had already settled in the land south of the Red River, in Oklahoma, on reservations. For a short time after the massacre, Chief Black Coal and the northern Arapahos continued following buffalo through traditional lands in eastern Wyoming, western South Dakota, western Nebraska, western Kansas (avoiding much of Colorado for obvious reasons). Eventually Black Coal made a deal with Chief Washakie of the Shoshone, and they settled on a reservation with them in the Wind River area of Wyoming.