The year:1876. The location: the Black Hills of South Dakota where a gold rush draws a throng of restless misfits to an outlaw settlement. Welcome to Season One of Deadwood...a hell of a place to make your fortune.
Seth Bullock abandons his position as Marshall in the Montana Territory to begin a career as a hardware merchant in Deadwood, Dakota Territory, a burgeoning, lawless gold-rush town set in the heart of Native land. Joining Bullock in the endeavor is his friend Sol Star. Before setting off from Montana, Bullock brings final justice to a horse thief, holding off dangerous mob to give him a legal hanging from a makeshift gallows in front of the sheriff's office.
As suspicions arise that "road agents" may have been the true perpetrators of the massacre, Swearengen takes a special interest in the health of its sole survivor, a young girl ministered to by the unlikely team of Doc Cochran and Calamity Jane. Meanwhile, Bullock and Star attempt to buy property from Swearengen, who suspects an alliance between Hickok and these hardware boys. At the Grand Central Hotel, Brom Garret rethinks his recent investment, while his wife Alma medicates her anxieties. And as a confrontation brews over the young survivor, Hickok asks Bullock to cover his back in a tension filled poker game.
Competition arrives for Swearengen in the form of the Bella Union, a new gambling outfit from Chicago operated by savvy Cy Tolliver, Madame Joanie Stubbs and gaming guru Eddie Sawyer. Hickok puts up precious collateral in a poker game with McCall; Bullock and Star strike a deal with Swearengen on a lot for their store and, with help from Hickok and Utter, set to building; Brom Garret threatens Swearengen with The Pinkertons before he and Dan Dority are dispatched to reconnect his claim of being the wildest man in the west.
As the body of Brom Garret is brought to camp, Alma immediately suspects foul play and asks doc Cochran for his opinion on how his death occurred. An old friend of Cy Tolliver, Andy Cramed, arrives into camp. Meanwhile Swearengen instructs Farnum to try and buy the claim back from Alma. Suspicious of his motives she asks Bill Hickock for help in the matter.
Swearengen transforms the Gem into a courtroom as Deadwood is forced to make its own laws to try a murderer; with Jane off on a bender, Swearengen employs Trixie to help Alma with the Metz Child; Doc Cochran fears Cramed's illness might threaten the camp; Tolliver sends Cramed to take air in the woods, where he meets Jane; and Bullock decides to take the law into his own hands.
Bullock encounters native resistance in his quest to bring a murderer to justice. Swearengen presses a resentful Farnum to keep tabs on Alma and Trixie; the camp fathers pool their resources to dispatch riders after precious vaccine and build a sick tent; Cochran enlists Jane as a nurse; and Swearengen collaborates on an article appearing in the Deadwood Pioneer (local newspaper).
After tracking down a murderer, Bullock returns to Deadwood a changed man--and a marked one--while Utter must pay final respects to a fallen friend. Dority and Stubbs both take special interest when teenagers Miles and Flora Anderson arrive in camp in search of their father, each finding work at a rival saloon; Calamity Jane earns her moniker in the Pest Tent; Swearengen sees through Trixie's latest subterfuge; and Alma remains cold on Farnum's inappropriately advanced bid on her claim.
Deadwood breathes easier when riders arrive with precious vaccine--and word of a possible treaty with the Sioux. Awaiting Trixie's return, a pragmatic Swearengen resists counsel from a bloody-minded Farnum; results of Bullock's assay of her gold claim moves Alma to reassess her plans and sets up a confrontation between Bullock and Swearengen; and Tolliver teaches Stubbs a deadly lesson at the expense of a couple of con artists.
With annexation looming, Swearengen calls a meeting to set up an informal government. Bullock and Alma compare notes on Ellsworth, and each other; Farnum gets a special-delivery letter from Hickok; Utter offers Jane a job; and Stubbs prepares to make a go on her own, with Tolliver's avowed blessings.
An opium theft leaves Swearengen trying to find common language with his supplier, as well as navigating tricky waters to deal with the mess. Meanwhile, Silas Adams, bagman for the magistrate from Yankton, arrives with bad news for Swearengen; Bullock regrets having raised his hand at the government meeting; Merrick proposes Deadwood's first "club"; and an unwelcome Rev. Smith gravitates to the Gem and its new piano.
Alma's father, Otis Russell, arrives from New York to "help" with her claim; Swearengen strikes a bargain with Adams to rid him of some legal baggage; Jewel journeys to Cochran's cabin for help with her leg; Utter hazards an opinion on the safety of Nuttall's saloon; Leon and Sawyer resume work at the Bella Union; Bullock is angered by the choice of a new sheriff; and Star winds up paying for a free service.
The U.S. Army--under General Crook a.k.a. "Custer's Avengers"--rolls into Deadwood, prompting a parade...and business solicitations from Farnum and Tolliver. Swearengen delivers a tortured soul from suffering; Bullock reacts decisively to Russell's intentions regarding Alma; Con Stapleton's new commission proves short-lived; Adams shows Clagett where his loyalties lie; and Bullock and Alma have a late-night meeting.