This 1940 adaptation of John Steinbeck's classic novel is one of Hollywood's most stirring tributes to the human spirit and most stinging indictments of greed and corruption in American life. That it was made at all is a credit to the courage of 20th Century-Fox production head Darryl F. Zanuck and director John Ford. They produced a timeless film that, despite changes to soften some of the political content and earthiness in the original, was hailed by Steinbeck as one of the best adaptations of his work. Even today, audiences find much to identify with in the plight of the Joad family, Oklahoma farmers who lose their land during the Great Depression and take off for California in search of work as migrant farmers. The unfair treatment they receive there turns their eldest child, Tom Joad (Henry Fonda) into an activist, which eventually puts him on the run from the law.

The novel's impetus came from "The Harvest Gypsies," a series of articles Steinbeck wrote for the left-wing San Francisco News in 1936 about the plight of migrant workers in California. That inspired him to create a fictional story designed to, in his words, "put a tag of shame" on those responsible for the Depression and the migrants' mistreatment. The Grapes of Wrath was actually the third novel in a trilogy about the effects of the Great Depression on California. It was preceded by In Dubious Battle (1936) and Of Mice and Men (1937). The Grapes of Wrath was the best-selling book of 1939, particularly popular among working class readers, and captured both the National Book Award and the Pulitzer Prize. As a result, Darryl F. Zanuck, production head of 20th Century-Fox, paid the then unprecedented sum of $100,000 for the film rights.

Zanuck's conservative leanings made Fox a strange choice for the film version. He was uncomfortable with some of the novel's political messages, which he had toned down in Nunnaly Johnson's screenplay. He also sent private investigators to infiltrate California labor camps to find out if condition were as bad as those depicted in the novel. The reports indicated they were actually worse. That vindicated his decision to make the film. He was still concerned about resistance from the Chase National Bank, which held the largest share of stock in Fox. As it turned out, Chase's president and his wife were huge fans of the book and supported the production wholeheartedly.

Helping him keep the film honest was Ford, another conservative moved by the Joad family's plight. When he read the novel, the Irish-born director was struck by how the Joads' struggles mirrored those of his own people. One simple step he took to keep the film realistic was to forbid the use of makeup or perfume on the set. He wanted his cast to look and smell like poor farmers. He did a good deal of location shooting in Oklahoma and California to capture the story. The art department found a beat-up 1926 Hudson "Super Six" truck for the Joads to drive. That was the same model described in the novel. To capture the sheer numbers of the homeless and unemployed traveling to California in search of work, the production paid drivers in the same straits as the Joads to form a caravan along the highway.

The role of Tom Joad was one of the most coveted being cast in Hollywood. Although there were stories indicating that Zanuck had tried unsuccessfully to cast Spencer Tracy, it was Henry Fonda, then still new to filmmaking, who won the role. At the time, Fonda was a freelance actor, having just finished a short-term contract with producer Walter Wanger. Knowing Fonda's potential as a film star, Zanuck threatened to give the role to Fox star Tyrone Power unless Fonda signed a standard seven-year contract with the studio. When later assignments at Fox proved less than thrilling, Fonda would come to regret the arrangement, but at least it landed him his most iconic role.

To avoid political controversy in California, Zanuck held the world premiere in New York, where The Grapes of Wrath received rave reviews and drew strong crowds. Although it did not rank among the year's top box-office films, it made back approximately twice its cost. The film may have been too controversial to win the Best Picture Oscar®, which went to Alfred Hitchcock's much less political Rebecca (1940). It won for Best Supporting Actress Jane Darwell, as Ma Joad, and Best Director. It also captured Best Film from the National Board of Review and the New York Film Critics. Steinbeck's novel has also inspired songs by Woody Guthrie and Bruce Springsteen, an award-winning stage adaptation filmed in 1991 and a 2007 opera with music by Ricky Ian Gordon.