Crawford H. Greenewalt was born in Cummington, Massachusetts, on August 16, 1902. He grew up in Philadelphia where he attended the William Penn Charter School before enrolling in the Massachusetts Institute of Technology, where he received a B.S. degree. In 1926 Greenewalt married Margaretta Lammot du Pont (daughter of Du Pont Company president Irňě du Pont). Greenewalt had begun his career at E.I. du Pont de Nemours in 1922 as a control chemist in the Philadelphia chemical works. He was soon promoted to group leader, research supervisor, and assistant director of research. As assistant director of the Chemical Department (1939-42), he set up the pilot plant for the production of nylon.

In 1942 when the Du Pont Company agreed to participate in the Manhattan Project, Greenewalt was named chief liaison, working with the physicists at the University of Chicago Metallurgical Laboratory, including Arthur Compton and Enrico Fermi, who were developing techniques for plutonium separation. In December 1942 the Du Pont Company signed an agreement with the U.S. government to design and construct a pilot plant-size reactor and to operate a plutonium production and separation facility. The site for this facility was to be in the desert of eastern Washington, and the plant became known as the Hanford Engineer Works. By the spring of 1945, Hanford was the site of a full-scale plant producing plutonium that would be used in the atomic bombs exploded in New Mexico on July 16 and over Nagaski, Japan, on August 9, 1945.

After the War, Greenewalt was named head of Du Pont's Explosives Department, and in 1948 he became president of the company, a position he held for 14 years. He died in 1993.