Marshall Harris Cohen was born in New Hampshire and graduated from high school in Baltimore. He earned a bachelor's degree in electrical engineering and a PhD in physics from Ohio State University. He continued to work at Ohio State in the Antenna Laboratory until 1954, when he accepted an appointment to Cornell in electrical engineering. As an early participant in the new field of radio astronomy, Cohen was associated with the founders of the discipline in England, Australia and in the US. While at Cornell he was closely involved in the building and operating of the Arecibo Telescope in Puerto Rico. After a brief appointment at the University of California, San Diego, from 1966 to 1968, Cohen moved permanently to Caltech as professor of radio astronomy. He was involved in all aspects of Caltech's radio astronomy program, which included the building of the first interferometer in the US in the Owens Valley; the establishment of a program in Very Long Baseline Interferometry (VLBI); and proposals for the contruction of a Very Large Array (VLA). In 1971, he was awarded the Rumford Prize of the American Academy of Arts and Sciences for his contributions to the development of VLBI.