Jurgis Rudkus and Ona Lukoszaite, a young man and woman who have recently immigrated to Chicago from Lithuania, hold their wedding feast at a bar in an area of Chicago known as Packingtown. The couple and several relatives have come to Chicago in search of a better life, but Packingtown, the center of Lithuanian immigration and of Chicago’s meatpacking industry, is a hard, dangerous, and filthy place where it is difficult to find a job. After the reception, Jurgis and Ona discover that they are more than a hundred dollars in debt to the saloonkeeper. In Lithuania, custom dictates that guests at a wedding-feast leave money to cover the cost, but in America, many of the impoverished immigrants depart from the feast without leaving any money. Jurgis, who has great faith in the American Dream, vows that he will simply work harder to make more money.
Jurgis, who is young and energetic, quickly finds work, as do Marija Berczynskas, Ona’s cousin, and Jonas, the brother of Ona’s stepmother, Teta Elzbieta. The family signs an agreement to buy a house, but it turns out to be a swindle; the agreement is full of hidden costs, and the house is shoddy and poorly maintained. As the family’s living expenses increase, even Ona and young Stanislovas, one of Teta Elzbieta’s children, are forced to look for jobs. Jobs in Packingtown involve back-breaking labor, however, conducted in unsafe conditions with little regard for individual workers. Furthermore, the immigrant community is fraught with crime and corruption. Jurgis’s father, Dede Antanas, finds a job only after agreeing to pay another man a third of his wages for helping him obtain the job. But the job is too difficult for the old man, and it quickly kills him.
Winter is the most dangerous season in Packingtown and even Jurgis, forced to work in an unheated slaughterhouse in which it is difficult to see, risks his life every day by simply going to work. Marija is courted by Tamoszius, a likable violinist, but the couple is never able to marry because they never have enough money to hold a wedding. Marija’s factory closes down and she loses her job. Distressed about the terrible conditions of his family members’ lives, Jurgis joins a union and slowly begins to understand the web of political corruption and bribery that makes Packingtown run. Hoping to improve his lot, Jurgis begins trying to learn English. Marija regains her job, but she is fired when she complains about being cheated out of some of her pay. Ona is now pregnant, and her job has become increasingly difficult for her. Her supervisor, Miss Henderson, oversees a prostitution ring, and most of the other girls at the factory are made to be prostitutes. Ona gives birth to a healthy boy, whom she and Jurgis name Antanas after Jurgis’s late father, but she is forced to return to work only seven days later.
In Packingtown, any mishap can bring ruin upon a family. Jurgis sprains his ankle and is forced to spend nearly three months in bed, unable to work. Even though poor working conditions caused the accident, the factory simply cuts off Jurgis’s pay while he recuperates. Unable to tolerate the misery, Jonas abandons the family, disappearing without a word. Kristoforas, the youngest son of Teta Elzbieta, dies of food poisoning. Jurgis at last recovers and returns to work, but the factory refuses to give him his job back. After a long, frustrating search for employment, Jurgis is forced to take a job at the fertilizer plant, the foulest place in all of Packingtown. He begins to numb himself with alcohol.
Ona is pregnant again. One night, she doesn’t return home from work, and Jurgis discovers that Phil Connor, her boss, kept her after work and forced her to sleep with him. Jurgis attacks Connor and is arrested. After an unfair trial, Jurgis is sentenced to a month in prison; the family will again be forced to scrape by without his wages. In prison, Jurgis befriends a criminal named Jack Duane. When he is released, Jurgis discovers that his family has been evicted from its home and is living at the run-down boardinghouse in which they first stayed when they arrived in Chicago. When he enters the boardinghouse, he finds Ona screaming; she is prematurely in labor, and the effort of giving birth kills her and the child. In agony, Jurgis disappears on a drinking binge.
At last, Teta Elzbieta convinces Jurgis to think of his son, and he again begins searching for a job. Through the philanthropy of a wealthy woman who takes an interest in the family, Jurgis finds a good job at a steel mill. He dedicates himself to Antanas and feels renewed hope in life. But his hopes are shattered when Antanas drowns in the mud-logged street. In despair, Jurgis abandons his surviving family members and wanders the countryside as a tramp.
In the winter, Jurgis returns to Chicago, where he finds a job digging freight tunnels. After injuring himself at work, he is forced to spend some time in the hospital. When he is released, he has no money and cannot find work, so he becomes a beggar. One night, a wealthy young man named Freddie Jones gives him a one-hundred-dollar bill, but when Jurgis asks a bartender to change it for him, the man cheats him, giving him ninety-five cents back. Jurgis attacks the man and is again sent to jail. In prison, he meets Jack Duane again. When the two men are released, Jurgis becomes Duane’s partner, and the two commit burglaries and muggings. Jurgis is eventually recruited to work for the corrupt political boss, Mike Scully. When a series of strikes hits Packingtown, Jurgis crosses the picket lines, undermining the efforts of the union but making a great deal of money as a scab.
One day, Jurgis sees Phil Connor again and attacks him. He is again sent to prison and, because Connor is a crony of Mike Scully, Jurgis’s meager political connections do not help him. After being released, he is forced to live on charity. By this time, Jurgis has completely lost touch with his family. One day, however, he meets an old acquaintance who tells him how to find Marija. He learns that Marija has become a prostitute to help support Teta Elzbieta and the children. She is also addicted to morphine. Jurgis wants to see Teta Elzbieta again but not until he finds a good job.
One night, his spirit all but crushed by privation and misery, Jurgis wanders into a socialist political rally, in which an orator delivers a speech that fills Jurgis with inspiration. Jurgis joins the socialist party and embraces its ideal that the workers—not a few wealthy capitalists—should own factories and plants. Jurgis finds a job as a porter at a socialist-run hotel and is reunited with Teta Elzbieta. He attends a socialist rally in which the speaker sums up Jurgis’s new beliefs: if more people convert to socialism, the speaker declares, then “Chicago will be ours!”