Jonathan van Olden Barnavelt is a magician who currently lives at 100 High Street in New Zebedee, Capharnaum County, Michigan, in the late 1940s and early 1950s. He is the next-door neighbor of Florence Zimmermann and, as of the summer of 1948, the guardian of his nephew, Lewis.
- Graduated from Michigan Agricultural College with an A.B. in Agricultural Science.
- Inherited a pile of money from his grandfather (who was around during the Civil War) and invested wisely in stocks and bonds, allowing him to live comfortably.
- Jonathan was admitted to the Capharnaum County Magician's Society on April 30, 1932, when he proved his abilities to other members of the Society by eclipsing the moon.
- Lived on Spruce Street, down by the waterworks, until he bought Isaac Izard's old house in 1943. Soon after moving in, he heard the sound of Isaac Izard's Doomsday Clock. At some point afterward, he bought a great number of clocks, using their ticking and ringing to drown out the sound of Isaac's clock.
- Converted the house to oil after buying it.
- Owns a piece of petrified wood from "out west".
- Owns a large, black 1935 Muggins Simoon.
- Created a magical illusion, the Fuse Box Dwarf, in the winter of 1948.
- Loved to get mail [The Figure in the Shadows; 29].
- Read in the tub [The House with a Clock in its Walls; 110].
- Knives make him nervous [The Figure in the Shadows; 19].
- Snores [The House with a Clock in its Walls; 82].
- Was interested in magic at an early age, and showed off his powers to a girl he liked, but it didn't work out. [The House with a Clock in its Walls; 177].