The Grapes of Wrath tells the story of the Joad family, tenant farmers from Oklahoma displaced during the Dust Bowl and Great Depression. Forced off their land by drought and bank foreclosures, they set out for California in search of work and dignity. Along the journey, they endure deaths, poverty, and disillusionment, only to discover that California offers exploitation and misery rather than opportunity.

Through the Joads' intimate story, Steinbeck reveals the larger plight of thousands of migrant families. Characters like Ma Joad symbolize resilience and the strength to hold the family together, while Tom Joad evolves from a recently released convict into a man inspired by Jim Casy's vision of collective justice, vowing to fight for the oppressed.