Kenneth Gage Baum (24 March 1891 – 2 April 1953) was the youngest of the four sons of L. Frank Baum and Maud Gage Baum. Kenneth was born on the birthday of his suffragette feminist grandmother, Matilda Joslyn Gage, and was named Gage in her honor. Baum dedicated his 1903 book The Enchanted Island of Yew to his son Kenneth.
Kenneth Baum moved to Hollywood, California in 1910, the same year as his parents. He married Dorothy Hilda Duce in 1914; they had two daughters, Frances Ozma and Janet. Their older daughter Ozma Baum Mantele was a prominent Baum family member of her generation. (Dorothy Duce Baum died on her daughter Ozma's wedding day.)
Though the youngest of the Baum brothers, K. G. Baum was the first to pass away, dying a month after his mother in 1953.