[3]: 23 He spent one year at Fargo University, after which he began teaching two classes at a primary school in Bottineau County, North Dakota.
[4] Ellis was offered a position as an assistant professor of history by the University of Missouri in 1929.
[3]: 117–118 In 1955, Ellis was appointed as the temporary president of the University of Missouri, and after seven months, he formally accepted the position.
[2] Prior to this promotion he served on the Department of the Army Historical Advisory Committee from 1954 to 1956.
Shortly after he became the university president, he began work as the co-chairman on the Missouri Committee on Education Beyond High School.