1930-01-14: marries Carol Henning.
1930-10: meets Edward F. Ricketts, marine biologist, philosopher, longtime friend.
1932-10: novel, The Pastures of Heaven, published by Brewer, Warren, and Putnam (New York).
1933-09: novel, To a God Unknown published by Ballou (New York).
1934: Gathers information on farm labor unions. Interviews labor organizer in Seaside.
1935-05-28: first popular success, Tortilla Flat, about Monterey's paisanos. Published by Covici-Friede (New York); beginning of lifelong friendship with editor Pascal Covici.
1936-10: novel, In Dubious Battle, about striking workers. Published by Covici-Friede.
1937-02-06: play-novelette, Of Mice and Men published by Covici-Friede.
1937: summer, first trip to Europe and Soviet Union.
1937-09: The Red Pony, three connected stories (later four), published by Covici-Friede.
1937-11-23: New York opening of the play Of Mice and Men (207 performances).
1938-04: Their Blood Is Strong, a nonfiction account of the migrant labor problem in California, published by the Simon J. Lubin Society (San Francisco).
1938-05: receives the New York Drama Critics Circle Award for the play Of Mice and Men.
1938-09: short story collection, The Long Valley, incorporating The Red Pony (1937), published by Viking (New York), where Pascal Covici became an editor after the bankruptcy of his own firm.
1939-04: The Grapes of Wrath, his greatest critical success, published by Viking, provoking both great popular acclaim and violent political condemnation for its depiction of Oklahoma migrants and California growers, as well as for its alleged "vulgar" language and Socialist bias.
1930-12: film of Of Mice and Men released.
1940-01: film of The Grapes of Wrath released.
1940-03-11 – 1943-04-20: marine expedition in the Gulf of California with Ricketts.
1940: spring, receives the National Book Award and the Pulitzer Prize for The Grapes of Wrath.
1940: summer, documentary film about living conditions in rural Mexico, The Forgotten Village.