William Harrison Clanton was an outlaw Cowboy in Cochise County, Arizona Territory. He, along with his father Newman Clanton and brother Ike Clanton, worked a ranch near the boomtown of Tombstone, Arizona Territory and stole livestock from Mexico and later U.S. ranchers.

Newman Haynes Clanton, also known as "Old Man" Clanton, was a cattle rancher and father of four sons, one of whom was killed during the Gunfight at the O.K. Corral. Two of his sons were involved in multiple conflicts in Cochise County, Arizona Territory including stagecoach robbery and cattle rustling. His son Ike Clanton was identified by one witness as a participant in the murder of Morgan Earp. Billy Clanton and Ike were both present at the Gunfight at the O.K. Corral in which Billy was killed. "Old Man" Clanton was reportedly involved with stealing cattle from Mexican ranchers and re-selling them in the United States. Records indicate he participated in the Skeleton Canyon Massacre of Mexican smugglers. In retaliation, Mexican Rurales are reported to have ambushed and killed him and a crew of Cowboys in the Guadalupe Canyon Massacre.