Steinbeck based "The Grapes of Wrath" on a true story that he read in Life magazine about a Joad family from Oklahoma.
I may have the name of the magazine wrong, but I heard a lecturer make that "true story" assertion decades ago.I have no idea why that memory popped up today, but ...
Is the assertion true?
I easily found this:
Steinbeck was known to have borrowed from field notes taken during 1938 by Farm Security Administration worker and author Sanora Babb. While Babb collected personal stories about the lives of the displaced migrants for a novel she was developing, her supervisor, Tom Collins, shared her reports with Steinbeck, who at the time was working for the San Francisco News. Babb's own novel, Whose Names Are Unknown, was eclipsed in 1939 by the success of The Grapes of Wrath and was shelved until it was finally published in 2004, a year before Babb's death.
...
Writing in Broad Street magazine, Carla Dominguez described Babb as "devastated and bitter" that Random House canceled publication of her own novel after The Grapes of Wrath was released in 1939. It is clear, she wrote, that "Babb's retellings, interactions, and reflections were secretly read over and appropriated by Steinbeck. Babb met Steinbeck briefly and by chance at a lunch counter, but she never thought that he had been reading her notes because he did not mention it." When Babb's novel was finally published in 2004, she declared that she was a better writer than Steinbeck. "His book," Babb said, "is not as realistic as mine."
https://en.wikipedia.org/wiki/The_Grapes_of_Wrath#Development
Which would indicate the story is an amalgamation of events that happened to different people.
According to wikipedia:
Steinbeck was known to have borrowed from field notes taken during 1938 by Farm Security Administration worker and author Sanora Babb. While Babb collected personal stories about the lives of the displaced migrants for a novel she was developing, her supervisor, Tom Collins, shared her reports with Steinbeck, who at the time was working for the San Francisco News.[9] Babb's own novel, Whose Names Are Unknown, was eclipsed in 1939 by the success of The Grapes of Wrath and was shelved until it was finally published in 2004, a year before Babb's death.
The Grapes of Wrath developed from The Harvest Gypsies, a series of seven articles that ran in the San Francisco News, from October 5 to 12, 1936. The newspaper commissioned that work on migrant workers from the Midwest in California's agriculture industry. (It was later compiled and published separately.[10][11])