"John Henry "Doc" Holliday" was an American gambling/gambler, gunfighter, and dentistry/dentist of the American Old West who is most well-known for his friendship with Wyatt Earp and his involvement in the Gunfight at the O.K. Corral.
As a young man, Holliday earned a D.D.S. degree from the Pennsylvania College of Dental Surgery and set up a dental practice in Atlanta, Georgia. In 1873, he was diagnosed with tuberculosis, the same disease that had claimed his mother when he was 15. He moved to the American Southwest in hopes that the climate would prolong his life. Taking up gambling as a profession, he subsequently acquired a reputation as a deadly gunman. During his travels, he met and became a good friend of Wyatt Earp and his brothers. In 1880, he followed the Earps to Tombstone, Arizona and took part in the Gunfight at the O.K. Corral.More Doc Holliday on Wikipedia.