Fentress took an unlikely route to architecture. The son of sharecroppers, he joined his parents in the North Carolina tobacco fields before dawn, putting in several hours of labor before school.
In the ninth grade, a drafting teacher noticed his talents for drawing and math, and suggested Fentress become an architect. After graduation from North Carolina State University he joined I.M. Pei’s architectural firm in 1972. Eight years later he started his own firm, but it wasn’t until 1987, when he entered a competition to design what would become the Colorado Convention Center, that his career took off. In 1989, Fentress and his partner, Jim Bradburn, were asked to submit a design concept for the Denver International Airport, a project that was already a year behind schedule and $75 million over budget. The architects' winning design would make Denver one of the most recognized airports in the world.