Early life
Born William Harrison Clanton, in Hamilton County, Texas, he was the second to last born of five brothers, the other four being John, Phin, Ike Clanton, and Alonzo. He also had two sisters, Mary and Ester. His father, Old Man Clanton, moved his wife Mariah and their six children to California after the end of the Civil War, where they moved several times over the next decade.

Move to Arizona
For more details on outlaws and ranching in Cochise County, see Cochise County in the Old West.

Billy moved with his family in 1873 to Pima County, Arizona Territory and then to Charleston. His father started the "Clanton Ranch" in 1877. In the same year prospector Ed Schieffelin discovered silver in the hills east of the San Pedro River on a plateau known as Goose Flats, less than 15 miles (24 km) from the Clanton ranch. The boom town of Tombstone grew within two years from less than 100 to more than 7000 residents.

Billy Clanton and his brother Ike often went into Tombstone on weekends, and Billy did business in Tombstone associated with the ranch, alongside the two McLaury brothers. By most accounts, Ike was not well liked in and around Tombstone because he was a drunk and a braggart. Billy was generally well liked and looked upon as hard working and level headed.

Livestock thefts
A few days after Wyatt Earp's arrival in Tombstone in December 1879, one of his prized horses was stolen. He heard several times that the Clantons had his horse. Almost a year later he got a tip that it had been seen at the Clanton's ranch near Charleston. Earp rode to their ranch and saw the horse being ridden down the street and placed in a corral. He stabled his horse at another corral and telegraphed James Earp in Tombstone to send up ownership papers for the horse to Charleston. Warren Earp brought the papers out that night. Earp testified in a later court hearing, "While I was waiting for the papers, Billy Clanton found out that I was in town and went and tried to take the horse out of the corral. I told him that he could not take him out, that it was my horse. After the papers came, he gave the horse up without the papers being served, and asked me if I had any more horses to lose."

In July 1879, several rustlers attacked a rancho in northern Sonora, Mexico, killing several of the inhabitants. Hunting the murderers, Mexican Rurales led by Commandant Francisco Neri illegally crossed the border into Arizona and were ambushed. Johnny Ringo later said that Old Man Clanton and his sons Ike and Billy were among the murderers.

On August 13, 1881, Billy's father was killed in an ambush Guadalupe Canyon by Mexican Rurales. The Clanton sons continued operating the ranch. On October 25, 1881, Ike, Billy, and the McLaury brothers headed to Tombstone after working to gather scattered cattle, lost during an earlier Apache raid. The events that transpired over that night and the next day have various versions.

Shoot out in Tombstone
Graves of Billy Clanton, Frank McLaury and Tom McLaury in Boothill Cemetery, Tombstone, Arizona.

Ike had repeated confrontations with the Earps and Doc Holliday. On October 26, 1881, events came to a head when Billy and Ike got together with Billy Claiborne and brothers Tom and Frank McLaury at the Dexter Corral. When they were seen in town "heeled" (armed), anxious citizens warned the Earps. Upon attempting to disarm the Cowboys, a shoot out broke out, later named the Gunfight at the O.K. Corral.

There remain today conflict versions of what actually happened and who fired first. Ike Clanton and Billy Claiborne ran away in the opening moments. Billy Clanton emptied his gun during the fight, and was killed along with both McLaurys. Doc Holliday and Virgil and Morgan Earp were wounded.

The town was divided, with many supporting the Clantons, and others supporting the Earps. The funeral that followed was the largest in Tombstone's history, with more than 300 people following the hearse and 2,000 watching from the city's sidewalks. The three Cowboys were buried in the Boot Hill cemetery. William McLaury, Frank and Tom's brother, tried to indict the Earps for killing the Cowboys. He wrote in a letter during the trial that two brothers and Billy Clanton were preparing to come to Fort Worth, Texas to visit after selling their cattle