Her first novel, Skitterbrain (1938), established her as a distinctive voice in children's historical fiction. Young Mac of Fort Vancouver (1940) transported readers to a fur-trading post in the Pacific Northwest, while Middle Sister (1945) offered an affectionate family story. One of her most popular books, Caroline and Her Kettle Named Maud (1949), blends humor and pioneer life in early Indiana and remains her best-known work. In addition to novels, Mason wrote accessible biographies of American heroes for young readers and contributed to popular series that brought history to children in classrooms across the country.
Mason's books are remembered for their lively heroines, accurate period detail, and gentle celebration of resourcefulness, making her a lasting contributor to twentieth-century American children's literature.