Marshall was born on May 7, 1928 in Sheboygan, Wisconsin to Lauretta (Jenkins) Cornell and George M. Cornell. Marsh lived in Sheboygan until graduating from Sheboygan North High School in 1946.

Enrolled in the U.S. Navy V-5 program at Stevens Point, WI from 1946-9, he was later transferred to the Pensacola (FL) Naval Air Station to complete his training. Marshall enlisted next with the U.S. Air Force, being stationed in Germany, Tripoli and stateside. After his service, he attended University of Wisconsin-Madison, achieving a degree in electrical engineering.

Marshall was married to Betty J. Gilbertson of Stevens Point, WI in 1957. Together with their three children, they lived in Madison, WI and Red Bank, NJ; before moving to Naperville, IL in 1967. Marshall was employed as an engineer by Western Electric Co., who later became Bell Laboratories, AT&T Technologies, then Alcatel Lucent. He led and served on numerous projects, receiving multiple recognitions, before retiring after 37 years. After retiring, he enjoyed time with his family, traveling, Kiwanis, and volunteering at a hospital. In 2010, Marshall and Betty moved to Fort Collins, CO.

Marshall is survived by his wife Betty, his children: Jon Cornell, Cathy Lemke (William G) and Richard Cornell; and his grandsons: William M. Lemke and Jon Cornell II.