After earning his undergraduate and doctoral degrees in chemistry from Harvard, Donald Hornig worked at the Woods Hole Oceanographic Institute and later at the Los Alamos Laboratory, before coming to Brown as assistant professor in 1946. He was promoted to full professor in 1951, when he was only thirty-one-years old.
He was Associate Dean of the Graduate School in 1951-52 , and served as Acting Dean the following academic year. He left for Princeton in 1957, where he later became chairman of the Department of Chemistry. In the 13 years between his departure for Princeton and acceptance of the Brown presidency, Hornig served as an advisor to Presidents Eisenhower, Kennedy, Johnson and Nixon.
President Hornig presided over the merger of Brown and Pembroke into a fully coeducational institution, as well as the development of a full M.D. degree-granting medical program. Another major but unpopular accomplishment was the improvement of Brown's financial position, which he achieved through cuts in spending. Hornig proposed selective cutbacks, including a 15% cut in faculty and the elimination of programs that did not enhance the overall standing of the University.
Students protested cuts in faculty, support services, and financial aid, and in July 1975, Hornig resigned, effective June 1976. He later described his presidency as "bittersweet." When asked what he would change about his administration, he replied, "The times."