Author Edna Ferber described the story of So Big as being about a "material man, son of his earth-grubbing, idealistic mother". Left an orphan at 19 years old in the late 1880s, Selina Peake needs to support herself. She leaves the city life she has known to become a teacher in the farming community of High Prairie, IL. Her father had told her that life is an adventure, and one should make the most of it.

Selina sees beauty everywhere, including in the fields of cabbages. She has a natural curiosity about farming and oversteps the woman's traditional role by having the audacity to ask the men questions. She soon marries Pervus DeJong, a farmer. Selina eagerly offers suggestions for operational improvements, but Pervus ignores her, preferring to use the unprofitable farming methods employed by his father.

Though she suffers many hardships, Selina always remembers the importance of beauty, and she admires those who exercise their creative talents. She tries to instill these views in her son Dirk and fights with her husband over the need for their child to get a full education. Once Dirk finishes college and starts work, will he retain Selina's values?

So Big was the first book to have the rare distinction of being the best-selling book of the year and win the Pulitzer Prize for fiction.