what social class does jurgis belong to? what criteria determine the class system?

If you are looking at Chapter 10 in particular, Jurgis and his family are pretty much at the bottom of the class system in America,

Chapter Ten marks a turning point for Ona Rudkus. Although her work in the factories is difficult, her hardships are compounded by giving birth and then being forced to return to manual labor so quickly. She develops an addiction to alcoholic elixirs, the only way she can cope with her work. Ona is the first character for whom the mental and financial hardships of her life are manifested in a physical way. Almost all of the main characters of the novel progress in this way. The hardships pressed upon the family by an unjust society become true physical hardships. Sinclair shows how poverty and powerlessness is not simply a mental or social hardship. It is a physical hardship as well.In terms of class, Jurgis and his family can't seem to get ahead no matter how hard they work .