Swearengen and his twin brother, Lemuel, were the eldest two of eight children of Dutch American farmer Daniel J. Swearingen and Keziah "Katie" Montgomery of Oskaloosa, Iowa. Swearengen remained at home well into his adult years and only arrived in Deadwood in May 1876, with his wife, Nettie Swearengen. Nettie later divorced him on the grounds of spousal abuse. Swearengen married two more times; both subsequent marriages also ended in divorce.
Deadwood
Swearengen originally owned and operated a canvas-and-lumber saloon in Deadwood known as the Cricket, which featured gambling and hosted prizefights. Shortly afterward, he closed it down and opened a larger saloon known as the Gem Theater. The Gem functioned as a saloon, dance hall, and brothel. Swearengen lured desperate young women to Deadwood, then forced them into prostitution through a combination of bullying and physical brutality committed by him and his henchmen. Calamity Jane, who was one of his first dancers at the Gem, procured 10 girls from Sidney, Nebraska for him on one occasion. The results were highly lucrative: the Gem earned a nightly average of $5,000, and sometimes as much as $10,000. The Gem burned down on September 26, 1879, along with much of the town, but Swearengen rebuilt his establishment larger and more opulent than ever, to great public acclaim. Swearengen's talent for making canny alliances and financial payoffs kept him insulated from the general drive to clean up Deadwood, including the otherwise successful work of Seth Bullock, the town's first sheriff. In 1899, the Gem burned down once again and was not rebuilt. The same year, Swearengen left Deadwood and married Odelia Turgeon.
Death
It is often reported that Swearengen died penniless while trying to hop a freight train, but research suggests he was murdered. According to his rediscovered obituary and contemporaneous newspaper accounts, Swearengen was found dead in the middle of a suburban Denver street on November 15, 1904, apparently of a massive head wound. Less than two months earlier, his twin brother Lemuel had been shot by unknown assailants and survived, although suspiciously not robbed.
From 2004 to 2006, the HBO television series Deadwood depicted Swearengen as a powerful and influential figure in the early history of the town, ruthlessly murderous and abusive, but ultimately guiding it towards its development and annexation to the Dakota Territory once he comes to see this course as fitting his best interests. The series altered Swearengen to be English-born. The English actor Ian McShane, won a Golden Globe Award for Best Actor in a Television Drama in 2005 for his portrayal of Swearengen. He was also nominated that year for Emmy and Screen Actors Guild Awards, and TV Guide named him #6 in their 2013 list of The 60 Nastiest Villains of All Time. The series also altered timelines; it shows the Gem as a going concern during the famous events of August 1876. McShane reprised his role of Swearengen in , which takes place in 1889, ten years after the series ended, and abandons any linkage to history. This time we see a much different Swearengen who has made peace with many from his past and is seen now as more of a community leader. Time has taken its toll on Swearengen, and throughout the film he is in declining health ending with his implied imminent death due to complications of liver failure. He leaves the Gem to his former prostitute Trixie. This is in contrast to the historical Swearengen's murder 15 years later.
