As early as December 1923, Struve defended his PhD thesis on short-period spectroscopic double stars at the University of Chicago. Frost helped him in waiving some required PhD examinations, e.g. in French and German, stating that Struve had done ample reading of scientific literature back in Russia, and was fluent in those languages. Struve then became an instructor (January 1924), assistant professor (1927) and full professor (1932) at the university. His rapid promotion was again assisted by Frost, who also used job-offer letters from other observatories to Struve as proof that Struve was a highly valued scientist who must be kept at the University of Chicago. Between 1932 and 1947, Struve headed Yerkes Observatory; from 1939 to 1950 he acted as a founding director of the McDonald Observatory, and from July 1, 1952 to 1962 served as the first director of the National Radio Astronomy Observatory at University of Virginia. All those years, he remained in America except for conferences and an 8-month sabbatical leave to the University of Cambridge between August 1928 and May 1929. He applied for and won a Guggenheim Fellowship to cover his travel to, and living expenses in, Cambridge. While in Cambridge, Struve mostly worked on interstellar matter; he also went on a short trip to Leiden to meet Jan Oort.