Frank becomes the first king of Narnia in C.S. Lewis’s The Magician’s Nephew.
Frank is a London cabman who is transported to the newly created Narnia along with Polly Plummer, Digory Kirke, and others. After Aslan creates the world, he chooses Frank to rule as King Frank I. Frank’s wife, Helen, later joins him in Narnia and becomes its first queen.
The novel explains the origin of several important Narnian features, including the creation of the world, the arrival of evil through Jadis, and the special significance of the wardrobe’s wood. Digory is the human child whose actions help bring these events about, but he does not become Narnia’s king.
The Magician’s Nephew was published in 1955 as the sixth Narnia book in publication order. Modern chronological editions place it first because its story occurs before The Lion, the Witch and the Wardrobe.