Thornton Wilder’s youngest sister, Janet Wilder (1910-1994), was the only Wilder child born in Berkeley, California. She attended schools in Berkeley and Oxford, England, and was graduated from New Haven High School in Connecticut. She then went to Mount Holyoke College, where she earned her B.A. degree in 1933, magna cum laude; she was also elected to Phi Beta Kappa. She earned an M.A. in biology in 1935, and completed a Ph.D. in zoology at the University of Chicago in 1939. She then returned to Mount Holyoke to teach.
In 1941, Janet Wilder married Winthrop Saltonstall (Toby) Dakin, an attorney and civic leader, and they lived in Amherst, Massachusetts. They had no children, and Janet devoted her energy to conservation issues, equestrians affairs, and animal rights. She wrote a book about raising a Morgan horse. At her death in 1994, she was remembered as “The First Lady of Amherst.”