Early life
Newman Clanton was born around 1816 in Davidson County, Tennessee, and married Mariah Sexton Kelso in Callaway County, Missouri on January 5, 1840. They had five sons and two daughters: John Wesley, Phineas Fay, Joseph Isaac, William Harrison, Mary Elise, Ester Ann, and Alonzo Peter. Alonzo Peter died as an infant. For almost twenty years, the family moved repeatedly, trying to find a place where employment or business could bring the family prosperity. Newman Clanton joined the California Gold Rush to California, but failed to find gold and returned east.

Move to Texas and Arizona Territory
By 1853, Newman had moved the family to Dallas, Texas, where they ranched for a time, and where their last two children, Ester and Alonzo were born. Both Newman and his oldest son John enlisted in the Confederate Home Guard at the outbreak of the American Civil War. Newman was eventually released due to his age. Newman moved the family to Arizona Territory in 1865 at the end of the war and settled for a time near Fort Bowie near Willcox, Arizona. In 1866, they moved to San Buenaventura, California and after 16 years of marriage his wife Mariah died. In 1871, he moved the family to Port Hueneme, California.

Ranching and smuggling in Cochise County
For more details on outlaws and ranching in Cochise County, see Cochise County in the Old West.
Two years later in 1873 Old Man Clanton and his children returned to the Arizona Territory. In 1877, Clanton built a large adobe house on land adjacent to the San Pedro River. The home became the headquarters of the Clanton Ranch. Phin obtained work as a freight driver. 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 family was very well situated to meet the demands for beef from the booming town of Tombstone. From its founding in March 1879, Tombstone grew from 100 residents to upwards of 15,000 citizens at its peak less than a decade later.

The Tombstone Mill and Mining Company opened a stamping mill about 5 miles from the Clanton's ranch in 1879 to take advantage of the ready water supply. Another mill soon followed and both began operations in 1879. The Clanton Ranch grew into a successful enterprise for many reasons. The Clantons also supplied beef to Bisbee and other nearby towns. During his testimony after the shootout at the O.K. Corral, Ike Clanton claimed to have raised and purchased about 700 head of cattle during the past year, and the Clanton ranch was one of the most profitable cattle ranches in that part of the country. However, the Clantons never registered a brand in either Cochise County or Pima County which was required to legally raise cattle. The Clantons were reputed to be among a group of outlaw Cowboys who crossed the border into Mexico where they stole cattle and re-sold them to the hungry miners in Cochise County. Tom and Frank McLaury worked with the rustlers buying and selling stolen cattle. The Mexican government at the time placed high tariffs on goods transported across the border, making smuggling a profitable enterprise.

The large numbers of men required to work the fast-growing mines led to a rapid increase in the demand for beef cattle. Although some of the cattle ranching was legitimate, the Clantons stole cattle from across the nearby border in Mexico. Clanton and his sons brokered the sale of the stolen animals in the United States. Other ranchers in the area like that owned by Henry Hooker raised their own beef in the relatively dry area around Tombstone, but required far more manpower to the same number of animals and protect them from Indian attack in the time it took to raise them.

Brothers John and Phin Clanton worked the family ranch. Phin was arrested several times for cattle rustling and once for robbery but was never convicted. During the early 1880s a number of outlaw Cowboys worked on the Clanton Ranch. These included Pony Diehl, "Curly Bill" Brocius, and Frank and Tom McLaury, until the McLaurys bought their own ranch. Johnny Ringo who had participated in the Mason County War, siding with Texas Ranger and gunman Scott Cooley, became associated with the Clantons.

First Skeleton Canyon massacre
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. The posse leader was executed. Johnny Ringo later said that he was among the murderers that included Old Man Clanton, his sons Ike and Billy, along with "Curly Bill" Brocius, Indian Charlie, brothers Frank and Tom McLaury, Jim Hughes, Rattlesnake Bill, Joe Hill, Charlie Snow, Jake Guage, and Charlie Thomas.

Move to Animas Valley, New Mexico
Clanton left his sons to run the San Pedro River ranch and moved to a new ranch in the Animas Valley of New Mexico, only a mile from the U.S.-Mexican border. This ranch served as a staging ground for cross-border cattle raids into Sonora, Mexico.

Second Skeleton Canyon massacre
Two years later, in July 1881, "Curly Bill" learned that several Mexican smugglers carrying silver were heading to the United States through Skeleton Canyon. He along with Johnny Ringo, Old Man, Ike and Billy Clanton, brothers Frank and Tom McLaury, Billy Grounds, and Zwing Hunt hid in the rocks above the trail. As the smugglers rode through the canyon the outlaw Cowboys opened fire and killed six of the nineteen men. They killed the rest when they tried to escape.

Guadalupe Canyon massacre
Main article: Guadalupe Canyon Massacre
On August 12, 1881, Clanton and six other men began a journey herding stolen cattle sold to him by Curly Bill through Gualadupe Canyon near the Mexican border.[11] Around dawn after the first day and night on the trail, they were ambushed by Mexicans dispatched by Commandant Felipe Neri. in what was later dubbed the Guadalupe Canyon Massacre. Five men were killed in the ambush, including Clanton who was cooking breakfast when he was hit, and fell dead into the cook-fire.

Survivors Harry Ernshaw and Billy Byers would survive to tell the story. Along with Dick Gray, who helped bury the dead, all said that the attackers were Mexican. The Byers family received from Ike and Phin Clanton a picture of Old Man Clanton on the back of which they had written, "Mr. Clanton killed on Aug 13—81 by Mexicans with 4 other Americans in Guadalupe Canon [sic] New Mexico." Both men signed the inscription. Another photograph of Will G. Lang, who was killed in the ambush, bears a similar inscription: "Will G. Lang killed by Mexicans—Animas Valley New Mexico Aug 13, 1881 together with Gray, Cranton, Clanton and Snow and Byers wounded."along with Behan's involvement in King's escape, was the beginning of increasingly bad feelings between the Earp and Cowboy factions.

Snow was buried where he fell due to decomposition. The others were taken back by wagon and buried about ten miles east of Cloverdale, New Mexico.

Reburial
In 1882 Ike and Phin Clanton exhumed their father's body and moved it to the Boot Hill cemetery in Tombstone, where he was re-interred alongside his youngest son, Billy Clanton, who had been killed two months after his father's death, in the Gunfight at the O.K. Corral. Both graves may be seen there today.

In the summer of 1887, Ike Clanton was indicted for cattle rustling and was killed resisting arrest in a gunfight with lawmen. His unmarked grave, near present-day Eaglecreek in Greenlee County, Arizona may have been located by a descendant in 1996. He unsuccessfully proposed to Tombstone town officials that the remains should be exhumed and reburied near Newman Haynes and Billy Clanton's graves at Boot Hill in Tombstone.

Newman's second son Phineas ("Phin") Clanton survived the cattle wars. He was convicted of cattle rustling and served 17 months in prison. After his release, he ran a goat ranch and married. He was involved in a wagon accident and his exposure to the cold weather led to a fatal case of pneumonia in 1905. He is buried in Globe, Arizona.