John Henry "Doc Holliday was a gambler and a gunman and loyal friend to Wyatt Earp. He was born in Georgia in 1851 and it is believed he graduated from a dental college in Pennsylvania or Maryland around 1872. He practiced dentistry for a short time in Atlanta and Griffin, Georgia. It was in the early 1870's that Doc developed his chronic cough and other symptoms of pulmonary tuberculosis, the same disease that killed his mother. He headed West to drier climate in 1873.
He then practiced dentistry in Dallas, Texas and took up life as a gambler. His games were poker and faro and from gambling and the drinking that ensued, he became involved in a number of gunfights. At one point, he was suspected of stagecoach and train robbery and after killing a bartender in a Las Vegas, Holliday moved to Tombstone and took up with Wyatt Earp. There is a story that Earp indicated Doc had saved his life once in Dodge City by coming to his rescue in a fight with cowboys. Holliday again practiced dentistry, gambling and maybe some stagecoach robberies while in Tombstone, even while Earp was deputy marshal.
By the time, Holliday had been married to "Big Nose" Kate Elder who signed a statement against him about a stage robbery that lead to his arrest. Holliday was out on bail when the famous O.K. Corral gunfight played out on October 26, 1881 with his help. He then accompanied the Earps from Tombstone to Colorado and was then arrested in Denver.
It was Bat Masterson, probably at the behest of Wyatt Earp, who intervened with the governor and got Holliday released. After a few more killings and arrests, Holliday went back to Glenwood Springs, Colorado where he died of his disease at the age of 36.