Yellow Horse was one of the Southern Arapaho chiefs in the early reservation period. He led part of the Arapahos on the Cheyenne and Arapaho Reservation in Indian Territory/Oklahoma and signed several treaties in the 1870s among other leaders like Little Raven, Left Hand, Big Mouth, etc.
Yellow Horse, Big Crow and Big Mouth were the three Arapaho leaders who seemingly were the most in favor of planting corn at the agency. In 1872 Yellow Horse was part of a delegation visiting Washington.
In June 1873, after several frictions at the reservation, Yellow Horse left Darlington Agency with 22 young warriors and joined Cheyennes at the Washita River who were holding a Sun Dance. These Arapahos took part in the Battle of Adobe Walls and several other raids in Kansas in June 1873.
See: “The Arapahoes, Our People” by Virginia Cole Trenholm, Univ. of Oklahoma Press, 1970