After arriving in the United States, his grandfather, James Castleton, worked as a gardener for Brigham Young, eventually saving enough money to establish his own business.

The youngest player on a club of seasoned veterans, Castleton gained national exposure with a perfect game against rival Akron, shutting them out at 4–0.

[2] The local media compared the feat to Cy Young's perfect game a year earlier, and Castleton quickly received offers from major league managers, including Clark Griffith of the New York Highlanders.

Once there, Castleton pitched formidably in the Southern Association, winning 10 of 13 decisions for Atlanta, despite earlier inactivity due to a sore arm.

[2] Continual health problems that evidently resulted from his 1908 illness impeded his performance, and he was forced to endure long periods of inactivity.

[2] While his later career was impeded by illness, Castleton was long remembered for his early performance in the Southern Association as well as his perfect game as a minor league pitcher.

[2] After retiring from baseball, Castleton returned to Salt Lake City, where he married Ester Adella Kjeldsen and established a lucrative practice as an accountant.