Ellsworth Spencer Gray was born to Elmer and Abbie Louse Ramsell Spencer in 1901 in Quincy, Massachusetts. In 1925, he earned his Bachelor of Science from the Massachusetts Institute of Technology (MIT), and in 1936, his Master's degree from Purdue University. He married Margaret Ethalind Cooper in 1928, and they had two children, David and Ann.

From 1926-1928, Gray taught as an assisant instructor in courses on thermodynamics and heat power at MIT before becoming an associate professor in mechanical engineering at the University of Missouri from 1929-1944. While at the University of Missouri, Gray taught Thermodynamics, Heat-Power Laboratory, and Heating and Air Conditioning. During this time he also earned a Hoffman Fellowship in Mechanical Engineering at Purdue University from 1935-1936. Gray and his family moved to Lawrence, Kansas in 1944 so Gray could become a professor of mechanical engineering and the chairman of the Mechanical Engineering Department at the University of Kansas (KU), a position he served in until his premature death from a heart attack in 1947.

While at KU, Gray was responsible for a $60,000 improvement of the heat-power laboratory at KU sometime in the mid-1940s. He taught classes in Thermodynamics, Steam Turbines, and Refrigeration and was an active member of Pi Tau Sigma, as well as a number of engineering academic societies.