The Polar Express theme is modeled after the Caldecott Medal-winning children’s book The Polar Express, written and illustrated by Chris Van Allsburg.

The very first Polar Express product was #33426, a box set with the Polar Express engine and tender, passenger car, a sleigh bell (which is significant to the story), and the audio book on cassette. Polar Express did not become an actual theme for BRIO until the early 2000’s so that original set is technically not part of it, but I list it here anyway because it makes sense to group them together.