The Master Key: An Electrical Fairy Tale is a 1901 novel by L. Frank Baum. It was published by the Bowen-Merrill Company of Indianapolis. The original edition was illustrated by Fanny Y. Cory, with twelve full-page color pictures plus smaller pen-and-ink sketches at the head and foot of each chapter. In that original edition, the book's title page bore this inscription, as a sort of sub-subtitle: Founded Upon the Mysteries of Electricity and the Optimism of Its Devotees. It was Written for Boys, but Others May Read It.