Upton Sinclair's The Jungle, written in 1906, is a fictionalized account of a Lithuanian immigrant named Jurgis Rudkus who attempts to make a living in the meatpacking industry in Chicago. The major theme of the book is that immigrants and other working-class people in America at the turn of the turn of the 20th century could not survive financially, physically, and morally with the back-breaking jobs available to them.
After his wedding, Jurgis tries to make a living in the filthy stockyards in Chicago, where cows were butchered and packed for sale, but he falls prey to con men. His wife is raped by her boss, and when Jurgis retaliates against this man, he is sent to jail. Eventually, his wife dies in childbirth, and he becomes an alcoholic. His only salvation is attending the socialist workers' rallies that teach him that workers must have a say and a share in their livelihood.
As stated above, the main theme of the book is that the jobs available to immigrants and the poor at the time did not allow these people to support themselves. They are still prey to con men and do not have the means to afford healthcare. The related theme is that American capitalism at the time did not work for the poor and that they needed a larger share in the profits, as well as access to cheaper and better housing, medical care, and food. In addition, the book calls attention to the hideously dirty conditions in slaughterhouses at the time.
The book resulted in major political and other changes, as Teddy Roosevelt, who was President at the time, sent investigators to look at the dirty conditions of the slaughterhouses and examine the safety of the meat that was sold from these places. As a result, the Congress passed the Meat Inspection Act and Pure Food and Drug Act of 1906. These acts made sure that meat was packed under clean conditions and that the food and drugs sold in this country were labeled correctly, were produced under sanitary and conditions, and were safe for consumption.