He entered the University of Chicago at the age of 16, earning undergraduate degrees in mathematics and astronomy in 1924.
[1] On June 13, 1929, Millis married Katherine Roseberry Wisner of Baltimore, MD, and together they had three children.
For the majority of his career, Millis held the position of president of Western Reserve University from 1947 under the federation with Case Institute of Technology in 1967.
He served as Chancellor of the new Case Western Reserve University, where he retired on June 30, 1969.
[2] Millis died of cancer at his home in Cleveland Heights, Ohio, on January 1, 1988.