Robert Franklin Gates was born on October 6, 1906 in Detroit, Michigan. He studied at the Detroit School of Arts and Crafts, and from 1929 to 1930 attended the Art Students' League in New York. Between 1930 and 1932, Gates studied under C. Law Watkins at the Phillips Gallery Art School in Washington, D.C., later becoming an instructor in life drawing and painting there. During this time, he met fellow student Margaret Casey, and they married on January 7, 1933. Between 1934 and 1938, Robert Gates was an art instructor at the Studio House in Washington, D.C.
In 1934, Gates received a commission from the U.S. Treasury Department Section of Fine Arts to create a series of watercolors of Charles Gardens, South Carolina, and from 1929-1940, murals for post offices in Bethesda, Maryland, Oakland, Maryland, and Lewisburg, West Virginia. In 1936, the Treasury Department also commissioned Gates and fellow artists Mitchell Jamieson and Prentiss Taylor to create series of watercolors of the Virgin Islands, arranging for several voyages there.
Between 1937 and 1942, Gates was a guest instructor at the University of Florida, taught art classes at Hood College in Frederick, Maryland and at the Washington County Museum of Art in Hagerstown, Maryland. He also taught at the Phillips Gallery Art School in Washington, D.C. while his wife was employed as the school secretary. In 1938, Gates received a summer scholarship to study under Henry Varnum Poor at the Colorado Springs Fine Arts Center.
During World War II, Gates worked as a civilian technician for the Navy Department doing model making and camouflage design, receiving the Distinguished Civilian Service Award for his work.
After the war, and the closing of the Phillips Gallery Art School, Gates attended classes taught by Bill Calfee at American University. In 1946, he joined the faculty and eventually becane chairman of the Art Department in 1954. Robert and Margaret Gates were divorced sometime in the mid-1950s. From 1966 to 1967, Gates was Artist-in-Residence at the U.S. Embassy in Baghdad, Iraq, under the Department of State Educational and Cultural Exchange Program. In 1967, he married his second wife, Sarita, while in Baghdad.
Gates is represented in the permanent collections of the American University, the Baltimore Museum of Art, the Corcoran Gallery of Art, the Dumbarton Oaks collection, the Phillips Collection, and the Lewisshon collection.
Robert Franklin Gates died on March 11, 1982 in Alexandria, Virginia.