 Marshall then earned a Juris Doctor from the University of Illinois College of Law in 1951.Marshall then served as a law clerk for Judge Walter C. Lindley on the United States Court of Appeals for the Seventh Circuit from 1951 until 1953.A Democrat, Marshall worked in private legal practice in Chicago from 1953 until 1967 at Johnston, Thompson, Raymond & Mayer (which later became known as Jenner & Block), becoming partner in 1961.