A mining camp in California during the gold rush, 1849-50. At dusk at the Polka Saloon, Nick, the bartender, pours drinks as the bar fills with boisterous miners ready to gamble. Outside, the distant voice of Jake Wallace, a traveling minstrel, is heard approaching; when he enters, the men join him in a song expressing the miners’ nostalgia for home. One of the younger miners, Jim Larkens, breaks down, homesick and unable to bear the harsh mining life. After the men collect money for Larkens’ passage back home, Ashby, a Wells Fargo agent, arrives to tell Sheriff Jack Rance that he is about to close in on the bandit Ramírez and his gang of Mexican highwaymen. As the bartender, Nick, serves drinks courtesy of Minnie – the Polka’s proprietress and, as the only woman in the camp, the community’s surrogate sister, mother, sweetheart and schoolteacher – Rance solemnly announces that she will soon be his wife. The miner Sonora jealously protests, and the ensuing brawl brings forth Minnie herself, who yanks Sonora’s gun out of his hand. The men calm down and sit to listen to her bible teaching.
Later, alone with Minnie, Rance tells her of his bitter life, empty of love and ruined by cards, and how he would wager everything to marry her. But she is not interested and, recalling her happy childhood in Soledad, explains the kind of love she hopes to find. Suddenly a handsome stranger enters, claiming to be Dick Johnson from Sacramento. Johnson and Minnie recognize each other: they met once on the trail to Monterey. Suspicious, Rance and the miners challenge his presence, but Minnie vouches for Johnson and further infuriates the jealous sheriff by dancing with him.
Just then Ashby drags in Ramírez’s accomplice, José Castro, who, recognizing Johnson, pretends to despise his leader and leads a posse on a false chase to his hideout. Before leaving, he whispers to Johnson—who is in fact Ramírez—that at the signal of a whistle to which Johnson should answer, the gang will attack the saloon and steal the miners’ gold. The men depart with Castro, and Minnie and Johnson are left alone. Minnie tells Johnson about her simple life and that she is still waiting for her first kiss. Nick interrupts and a whistle is heard. Johnson ignores it, for he is already in love with Minnie, who tells him that she would protect with her life the gold the miners have left in her trust. She shyly invites him to visit her in her cabin later that evening and he accepts. After he leaves the saloon, the girl muses ecstatically on his words of love.
In Minnie’s cabin in the mountains, her Native American servant Wowkle sings a lullaby to her baby as the father, Billy Jackrabbit, comes to propose marriage. Soon Minnie enters and excitedly gets dressed for Johnson’s visit. When he arrives, full of compliments and advances, she begs him to slow down, but soon forgiving him, tells him of her joy for life. After Wowkle leaves, he takes Minnie in his arms and kisses her. Johnson, full of doubt as to how to tell her about his true identity, is about to leave, but a mounting snowstorm leads Minnie to suggest that he stays the night. She offers him her bed and prepares a place for herself in front of the fire. When there is a loud knocking at the door, Johnson hides. Rance, Ashby, Nick and Sonora, checking to see that Minnie is safe, tell her that they have discovered that Johnson is Ramírez. Shocked, she claims to know nothing and sends the men away. She then angrily confronts Johnson, who tries to explain what made him become a criminal and declares that when he met her he decided to give up his former life. Deeply hurt, Minnie sends him away. He goes, but a shot rings out, and his body falls against the door. Overcome by pity and love, Minnie drags him back into the cabin and hides him in the attic. Rance returns, convinced that Ramírez is in the cabin, but his search reveals nothing. The sheriff again expresses his love for Minnie and declares no one else will have her. As she defies him, a drop of blood falls on his hand from above. Johnson is forced to surrender, but Minnie, knowing the sheriff’s passion for gambling, challenges Rance to a game of poker. If he defeats her, he wins her honor and her lover’s freedom; if he loses, Johnson goes free. Minnie cheats and wins. Rance leaves.
clearing in the forest. Johnson has been nursed back to health by Minnie and is now again on the run. By a dawn campfire, Rance, Nick and some miners are waiting while Ashby and the Wells Fargo men track down Johnson in the hills. Rance and Nick discuss bitterly Minnie’s love for the bandit. A group of miners appear, having spotted him trying to make his escape on the other side of the mountain. Ashby and his men bring the bandit to Rance, who decides to hang him. Johnson begs one last favor—that Minnie believe him free and starting a new life elsewhere. Just as the noose is about to be slipped around his neck, Minnie rides to the rescue. Holding the mob at bay, she reminds them of her years of devotion, in return claiming Johnson as her own. As Rance leaves in disgust, the miners give Minnie what she asks. With sadness on both sides, they bid farewell to Minnie and Ramírez, who ride off to start a new life together.