Based on Richard Llewellyn's 1939 novel of the same name, How Green Was My Valley follows the blue-collar Morgan family, a salt-of-the-earth clan in South Wales at the turn of the 20th century. The story is told from the perspective of the youngest son, Huw (Roddy McDowell), who's wistfully reflecting back on the events of his childhood from the vantage point of old age. Much of the dramatic action centers around the colliery at the far end of town, where all the local men try to earn their livings. Men from a nearby ironworks, who are willing to work for next to nothing, have taken positions at the coal mine, driving down pay for everyone else. God-fearing patriarch Gwilym Morgan (Donald Crisp) wants to believe that the owners of the mine have the best interests of the workers at heart, but his grown sons aren't blind to the financial realities. They form a union against their father's wishes and go on strike, but the influx of cheap labor has already taken its toll. Many of the men lose their jobs, those who remain no longer earn a living wage, and the town will never quite be the same.

Producer Daryl F. Zanuck bought the film rights to the novel for about $300,000 with the intention of making it into a four-hour epic to rival the blockbuster success of Gone with the Wind. William Wyler was originally set to direct How Green Was My Valley in technicolor on location in Wales. He even courted Laurence Olivier, Katharine Hepburn, and Tyrone Power for roles in it, and was also responsible for casting Roddy McDowell as Huw. However, Wyler ended up leaving the project to make The Little Foxes while John Ford, who at the time was just coming off of directing a film adaptation of the John Steinbeck novel, The Grapes of Wrath, took over. Shooting in Wales was deemed impossible to do so during World War II, so Ford had the studio, 20th Century Fox, build an 80-acre authentic replica of a Welsh mining town in the Santa Monica Mountains near Malibu, California. Due to the color of flowers in Southern California not matching those found in Wales, the film had to be shot in black & white.

After premiering in New York City on October 28th, 1941, How Green Was My Valley continued to expand to more movie theaters all over the world over the course of several months. The film was able to gross over $2,400,000 at the worldwide box office on a budget of $800,000, making it the fourth highest-grossing release of that year. On February 26th, 1942, How Green Was My Valley ended up winning 5 Academy Awards for Best Picture, Best Director (John Ford), Best Supporting Actor (Donald Crisp), Best Art Direction-Black & White, and Best Cinematography-Black & White. Nowadays, it gets a lot of undeserved flack, mainly because it famously managed to beat what is considered to be one of the greatest movies of all time, if not, the greatest, Citizen Kane. Though in the years since, How Green Was My Valley has been considered to be a classic in its own right, especially among John Ford's legendary filmography.