At the top of a California mountain, Cullen Bohannon and a group of Central Pacific surveyors discover the route to Utah: “Straight through the coal fields of Weber Canyon” and the Nevada desert.

Cullen rides ahead of Chinese workers trudging through snow. Tao, their foreman and translator, evades questions about Chang, the opium den and whorehouse owner who imports Chinese laborers. Tao‘s son, Fong, says Chang steals half the Chinese payroll.

Over dinner with James Strobridge, the Central Pacific’s foreman, Cullen tells Collis Huntington about Chang’s deception. Huntington argues that it doesn’t concern them.

In a Mormon tent on the Central Pacific grounds in Truckee, Brigham Young’s son, Phineas, confesses to The Swede that his father has lost faith in him. The Swede responds, “I believe in you, brother.”
Huntington hands Cullen a telegram from Brigham: Cullen’s family was banished and “could be anywhere.”

After Cullen demands Chang stop skimming wages, Chang’s henchmen retaliate by giving Tao a brutal beating.

Huntington and Cullen butt heads over how to deal with Chang. Huntington is more concerned about Durant‘s rapid progress with the Union Pacific.

Huntington’s office manager, Samuel, secretly telegraphs Durant in Laramie, informing him that Cullen has found a route to Weber Canyon.

The Swede reveals himself to Cullen. He thanks Cullen for “revealing the truth” — that Brigham Young is a false prophet and The Swede is the One True Prophet.

Cullen plans to use the Sacramento, an abandoned locomotive, to mechanize removal of rock from the tunnel they’re drilling through the mountain.

With Tao recovering and unable to work, Cullen hires Fong as his new translator.

The Mormons refuse to work without proper winter provisions. When Brigham denies Phineas’s request for supplies, The Swede consoles Phineas, then buys boots for the Mormon workers and tells them it’s an answer to Phineas’s prayers. Later, The Swede shows Phineas a shortfall in the funds they’ve received from Salt Lake City. Phineas believes Brigham is cheating them and asks The Swede for advice.
Fong is injured when the brake snaps on the sled hauling the Sacramento up the mountain. He devises a method to anchor the sled to trees for a controlled descent.

The next morning, Cullen finds Fong coughing up blood. Cullen lifts Fong’s shirt to reveal bandages wrapped around his torso above a large wound. Cullen holds Fong down to re-wrap the wound, slices through the bandages, and recoils in shock: Fong is a woman. “Please don’t say about this,” Fong pleads, “They kill me.” Cullen instructs Fong to stay in the tent.

Cullen works with the Chinese lowering the sled down the mountain, but it careens out of control when an anchor tree falls. Fong races to help.

While stopping the sled, Fong and Cullen are tossed down a steep slope. They tie themselves together with rope just as the snow gives way beneath Fong. Dangling over the cliff edge, Fong cuts the rope.
Strobridge gets the Sacramento to the tunnel while Cullen rescues Fong. She reveals that her real name is Mei and that Chang works for the same rebel leader she escaped from in China.

Later, Huntington applauds the progress Cullen’s mechanized steam shovel is making. However, the machine makes three Irish workers obsolete — they are demoted to Chinese-level work. In retaliation, they lynch Chang. Tao and Cullen cut Chang down just in time to save his life.

Chang asks Huntington for justice. Huntington proposes a trial, but finds out “Chinamen ain’t allowed to testify against white men under California law.” Cullen exiles the Irishmen, but Chang also demands a 2 percent stake in the railroad. When Cullen refuses, Chang has his workers strike. In return, Cullen holds the Chinese supplies hostage. Tao ends the strike by getting the Central Pacific to ship the Chinese dead back to their home villages as a show of respect.

Inside the Union Pacific office, Samuel shows Durant the Central Pacific’s new route through Utah.

Outside, Delaney tells Louise he’s working on a bridge across Salt Lake that Durant never intends to build.

The Swede tells Phineas he’s had a vision: Phineas is to be the new prophet.

Durant advises Maggie to buy Cheyenne land. Once Laramie prices have skyrocketed and Cheyenne prices have bottomed, he’ll declare Cheyenne again as the railroad hub and they’ll both profit.

Chang secretly hires a traveling salesman to kill Tao. Cullen agrees to transport Mei and her father’s coffin to San Francisco on a supply wagon when their train breaks down en route. The wagon breaks crossing a river. Cullen helps Mei, wearing her mother’s dress, bury Tao in the woods. She tells Cullen how she escaped a life of prostitution with the Sze Yup company in China.
Brigham accepts a stolen map showing Huntington’s railroad bypassing Salt Lake City, as down payment on the half-million dollars Durant owes for the Mormon graders. Brigham calls his workers home from the Central Pacific.

Louise writes an article exposing the Union Pacific’s falsification of plans in order to deceive the Mormons. President Grant orders both railroads to establish a route and terminus.

Brigham tells Cullen the location of his family in exchange for advocating for Salt Lake City as the terminus. Cullen actually proposes no terminus at all, with both railroads bypassing Salt Lake City and the prized coal fields of Ogden going “to the man who gets there first.” Grant agrees.

Eva kills Josie after Josie steals from the whorehouse and conspires to take her place as Madame.

Phineas stabs Brigham and announces that he is the True Prophet, but fails to kill his father and is taken into custody. Cullen explains that Phineas was corrupted by The Swede, who’s escaped and is headed towards the Hatches.

The Swede kills Naomi’s father and sister and injures her new husband, Isaac, before chasing Naomi and William into the woods. Cullen pursues and saves them, knocking The Swede unconscious after being shot in the leg.

Cullen brings The Swede to Camp Douglas, where he is tried and sentenced to hang. Cullen watches him die.

Cullen goes back to the Hatch homestead. Isaac tells him they’re moving to Salt Lake City. Cullen insists on seeing them safely there.

Durant buys Irish workers from Mickey to replace the Mormons he lost after double-crossing Brigham. He pays in Union Pacific stock.

In Salt Lake City, Cullen informs Brigham of The Swede’s death and convinces him to accept Naomi and Isaac back into his “flock.” Cullen tearfully bids goodbye to William.

Cullen rides back to Truckee, where Mei embraces him and they make love.

After the workers fall behind, Cullen proposes using nitroglycerine to make up the time. Strobridge warns of the danger but agrees to help. However, he refuses to help Cullen sweep the tunnel for unexploded charges so Huntington fires him.

When Cheyenne is named the official railroad hub, enraged Laramie ranchers order Durant to pay back their lost investment. Penniless, Durant concocts a plan to have Mickey kidnap him and split a $250,000 ransom from the railroad board, but the scheme goes wrong and Shea kills both Delaney and Maggie. Left with no choice, Mickey kills Shea.

Wai-Ling reveals Mei’s identity to Chang. Cullen finds out and puts Mei on a stagecoach out of town, promising to come for her as soon as he’s dealt with Chang.

Cullen tries to buy Mei’s contract from the Sze Yup company, but Chang refuses to sell. Meanwhile, Chang’s men ambush Mei’s stagecoach and she escapes to Washoe City. Chang pursues her and they meet in a saloon. Mei aims her pistol at Chang, but Cullen bursts in and kills Chang first. On the ride home, Mei tells Cullen she’s going back to China. Later, she slips out and leaves behind a note with an address in Ningpo.

In Ogden, the final Hell on Wheels tent towns are assembled. Campbell buries a stake in the center of the grade. Ogden and the $2.5 million left in government railroad bonds go to whoever reaches it first.
Workers from both lines defect, following a man Cullen and Mickey discover to be Strobridge offering work past the railroad’s completion. Cullen fails to convince Strobridge to release his men, but Mickey resorts to violence and forces his workers to return.

The next morning, the Chinese workers return out of respect to Cullen. The Union Pacific has 10 miles left while the Central Pacific has only six, and “ain’t no man ever laid 10 miles of track in one day.”

Through the day, the Central Pacific gains ground. Durant points at the finish line, gives an impassioned speech about how much he’s sacrificed “to get you here,” and shouts for the men to “return the favor.” Instead, the freedmen desert the Union Pacific and join Cullen to help the Central Pacific cross the finish line first.

In one last ploy, Durant insists that Campbell verify the track’s integrity before awarding Huntington the win. Huntington caves – he keeps the bonds and gives Ogden to Durant.

Durant drives home the Golden Spike. Afterward, Campbell charges Durant with bribery, fraud and corruption, then summons Cullen to testify against Durant in Congress. Before heading to Washington,

Durant buys out Mickey’s stake in the Union Pacific. Mickey heads to San Francisco to start anew.

Louise offers Eva a book deal to tell her life story as a way in to “society.” Eva considers the offer but ultimately decides she’s “done whoring,” and cashes out her share of the saloon.

At a Washington gala celebrating the railroad’s completion, Durant is ostracized while President Grant offers Cullen a position in the United States Army. Cullen initially accepts, but changes his mind upon realizing the job would be mostly killing Indians.

During the hearing, Cullen refuses to indict Durant and maintains that “the transcontinental railroad could not have been built” without him. Durant offers himself up to the committee’s whims, “for history is written in pencil and the truth carved in steel across this nation.”

At the Central Pacific depot in San Francisco, Cullen heads towards Huntington but walks past him and boards a ship to China, turning his eyes to the future.