Complex sentence: He briefly worked as a Research Fellow at the Cowles Commission before joining faculty at Iowa State College, where he was promoted professor in 1946 and remained until 1962, when he resigned to join the staff of the University of Pittsburgh.
Split into simpler sentences: He briefly worked as a Research Fellow at the Cowles Commission before joining faculty at Iowa State College, where he was promoted professor in 1946. He remained at Iowa State until 1962, when he resigned to join the staff of the University of Pittsburgh.