Herzfeld moved to The Catholic University of America in Washington, DC, where he remained until his death in 1978. He received emeritus status in 1969 and stayed active for the rest of his life. Reasons for Herzfeld leaving Johns Hopkins were described in a letter to Arnold Sommerfeld. A main reason was the dire financial situation at Johns Hopkins. However, there were other reasons as well. One being his relationship with R. W. Wood, a professor of experimental physics and chairman of the physics department, had deteriorated. Also, J. A. Bearden, another experimentalist, thought there was too much emphasis on theoretical physics and the number of German physicists in the small department was out of balance. Bearden also suspected that Herzfeld had brought Franck to Johns Hopkins to further Herzfeld's ambitions to be department chairman. Finally too, Bearden thought Herzfeld had caused dissension in the department over his strong support to promote Göppert-Mayer from research associate in physics to a regular faculty appointment. While Herzfeld did receive offers from both Fordham University and Catholic University, neither was appealing as they did not have strong research departments. While talking the situation over with Isaiah Bowman, president of Johns Hopkins, it became clear that the financial difficulties at Johns Hopkins might require downsizing the physics faculty. With this in mind, Herzfeld accepted the offer from Catholic University. Herzfeld's teaching responsibilities and salary at Catholic University were about the same as that at Johns Hopkins, but there were additional administrative duties, as he was also chairman of the physics department. In the late 1940s, Herzfeld increased the attention at Catholic University to quantum-mechanical calculations on the electronic structure of polyatomic molecules, thus establishing a respected position for the University in this field. In 1959, Herzfeld and Theodore A. Litovitz collaborated on a book, in part, summarizing Herzfeld's thinking on ultrasonics over the 30 plus years since his article with F. O. Rice. In 1966, Herzfeld published a review article summarizing 50 years of developments in physical ultrasonics. Personal life In 1938, Herzfeld married Regina Flannery, who was an instructor of anthropology at Catholic University; by the time she retired in 1970, she had risen to professor and the first woman to head that department. Herzfeld was a Catholic who had a profound interest in Catholic theology. He received the James Cardinal Gibbons Medal for his contributions to the United States, the Catholic Church,