The budget for the film was $750,000.
The film shot for seven weeks.
The film was one of the first to be voted onto the National Film Registry (1989).
The novel's original ending was far too controversial to be even considered for a film in 1940. It involved Rose-of-Sharon Rivers (Dorris Bowdon) giving birth to a stillborn baby and then offering her milk-filled breasts to a starving man, dying in a barn.
The pro-union stance of the film led to both John Steinbeck and John Ford being investigated by Congress during the McCarthy "Red Scare" era for alleged pro-Communist leanings.
The production had a fake working title, "Highway 66", so that the shoot of the controversial novel would not be effected by union problems. Much of the dire straits portrayed in the film continued during and after the release of the movie.
The truck used in the movie is a 1926 Hudson "Super Six" - the same model as in the book.
Unusual for John Ford, he allowed Darryl F. Zanuck to supervise the editing. Indeed, Zanuck remains one of the very few producers to actually draw praise from the normally rather critical director.
When Darryl F. Zanuck suggested to John Ford that, to create an upbeat ending, he use Ma Joad's "we're the people" monologue for a closing scene, Ford told Zanuck to direct it himself - which he did.
While filming the Joads' car traveling down the highway, John Ford wanted to add a shot showing the large number of caravans heading west, so the film's business manager stopped actual cars making the trek and paid the drivers five dollars to escort the Joads' jalopy for the cameras.