[2] Simultaneously, Gabriel was hired as a general editor of The Pageant of America, an eventual 15-volume series of pictorial history of the development of the United States.
[1] Fellow professor William Robert Hutchison cited Gabriel as a mentor in the history department and called him a "perennial teacher and friend".
[9] He would go on to serve as director of Yale Studies for Returning Service Men from 1944 to 1946 and lecture at the United States School of Military Government.
[11] Gabriel was upset that Yale accepted a $500,000 donation on the condition the department focus on "the fundamental principles of American freedom in the field of politics and economics in order to combat the meaning of foreign philosophies".
[16] In 1975, he was the recipient of the Wilbur Cross Medal for "distinguished achievements in scholarship, teaching, academic administration, and public service".