He married Mary Constance Edwards on July 3, 1912, in Santa Clara, California.

[1][3] His dissertation, advised by Fernando Sanford, was titled, Determination of Peltier Electromotive Force for Several Metals by Compensation of Methods.

[6] He was a member of the Central Presbyterian Church of Eugene and a trustee of the Westminster Foundation.

He joined the faculty at the University of Oregon, serving there between 1914 and 1949, and researching the properties of metals.

[1] During World War II Caswell served on staff at the MIT Radiation Laboratory, where he led a section that produced instructional handbooks for prototype radar sets.