Ellis Albert "Al" Swearengen (b. Oskaloosa, Iowa, 8 July 1845 – d. Colorado, 15 November 1904) was a pimp and early entertainment entrepreneur in Deadwood, South Dakota, running the Gem Theater, a notorious brothel, for 22 years, and combining a reputation for brutality with an uncanny instinct for forging political alliances.
Swearengen was one of the first Deadwood residents not to be a prospector or miner; he represented the beginning of a second wave of residents, attracted there by the promise of riches to be stripped not from the earth, but from the prospectors and miners. He built a small saloon called the Cricket Saloon, which featured as entertainment in its close spaces local miners engaged in what were advertised as "prize fights", although no prizes were actually awarded. Within a year, Swearengen had accumulated enough money to build the much larger and more opulent Gem Variety Theater, which opened on April 7, 1877, featuring the now traditional "prize fights" in addition to stage shows, and, mainly, prostitution.
Swearengen lured desperate young women from far away to Deadwood, then forced them into prostitution through a combination of bullying and physical brutality, by himself and his henchmen. The results were highly lucrative, the Gem bringing in an average of $5,000 a night, sometimes as much as $10,000 (between $140,000 and $280,000 inflation adjusted for 2009). When it burned down along with much of the town on September 26, 1879, Swearengen rebuilt it larger and more opulent than ever, to great public acclaim. Swearengen's talent for canny alliances and financial payoffs kept him insulated from the general drive to clean up the town, including the otherwise successful work of Seth Bullock, until the Gem burned down once again in 1899. He was remarried the same year to Odelia Turgeon. It appears that the Methodist church in Deadwood - which also took a moralist crusade to clean up the town - specifically targeted the Gem Theater.
According to his recently rediscovered obituary, Swearengen was found dead in the middle of a suburban Denver street on November 15, 1904. He apparently died of a massive head wound and was not hopping a freight train as is often reported.