Katherine Paterson lived for a time in Takoma Park, Maryland, a suburb of Washington, DC. The novel was inspired by a tragedy of that time: on August 14, 1974, her son David's best friend, Lisa Christina Hill, died after being struck by lightning in Bethany Beach, Delaware. She was 10 years old. There is a tree dedicated to her in a memorial outside Takoma Park Elementary School (pre-K to second grade), which she and David attended. Sligo Creek, which runs through Takoma Park, may have provided inspiration, too.
The name of the imaginary kingdom is similar to that of the Narnian island Terebinthia, created by C. S. Lewis in 1951 or earlier for Prince Caspian and The Voyage of the Dawn Treader. Paterson observed in 2005:
- "I thought I had made it up. Then, rereading The Voyage of the Dawn Treader by C. S. Lewis, I realized that I had probably gotten it from the island of Terebinthia in that book. However, Lewis probably got that name from the Terebinth tree in the Bible, so both of us pinched from somewhere else, probably unconsciously."
It makes a direct reference to The Chronicles of Narnia as a set of books that Leslie lends to Jesse so he can learn to behave like a king.