Salt of the Earth has the distinction of being the only film blacklisted by the United States government. It is the story of Ramon Quintero (Juan Chacon) and his wife Esperanza (Rosaura Revueltas), who live in a small mining town in New Mexico in the 1950s. They endure poor working conditions, have no hot water, and the wages between Mexican-Americans and caucasians are grossly different. Ramon and his co-workers go on strike, and the film follows the progression of the family and community as the strike takes its toll.

Ramon emerges as a leader for his union and at one point is falsely arrested and brutally beaten by local authorities. After many months of striking, an injunction forces the male workers to make a choice: either give up the strike and go back to work or be arrested and spend time in prison. The wives of the workers step up and use a loophole in the injunction to allow for the women to jump into the picket line. Local authorities begin to use threats of violence against the women, including tear gas attacks and running a car into a crowd of the wives. The women remain strong and unified, even when authorities arrest the women and keep them and their children in prison.

This film was way ahead of its time, advocating equal rights for all races, all genders and all social classes. Director Herbert J. Biberman was one of the "Hollywood Ten" who served jail time for contempt of Congress during the House Un-American Activities Committee hearings. Because of the film's association with many blacklisted individuals, production of the film had to be moved when members of the crew were issued death threats by local citizens. This was also the last American film to star Rosaura Revueltas, who was branded as a communist and deported to Mexico.

Near the end, a role reversal has occurred where the men stay home, do laundry and raise the children where they gain a new found appreciation for the duties their wives have quietly performed all these years. The women are no longer shadows behind their husbands and have stepped up into a role where they gain equal footing with men.