James Harold Dunn, oilman, the son of Charles Allen and Charlotte (Webb) Dunn, was born on April 22, 1904, on a farm near Lancaster, in Dallas County. He and his brother spent their early years in Dallas, where he graduated from Oak Cliff (now Adamson) High School in 1921. After entering the Agricultural and Mechanical College of Texas (now Texas A&M University), he worked his way through college, then returned to Dallas, where he worked for the next thirteen years for the Lone Star Gas Corporation and became the company's chief production engineer. He married Louise McCallum of Garland in 1928, and they had a daughter.
In 1938, after receiving his master's degree in civil engineering at Texas A&M, Dunn joined the Shamrock Oil and Gas Corporation in Amarillo and was made manager. Under his leadership, Shamrock became a leading distributor of petroleum products and eventually was pulled out of the red. Dunn was concerned about the wasteful use of natural gas, particularly in the production of carbon black (see CARBON BLACK INDUSTRY), and often lobbied in Austin for the passage of needed conservation measures. He proposed the construction of the recycling plant in the Opelika Reservoir at Murchison, in Henderson County; the plant would strip gas of its liquid and return the dry residue gas to the ground to save it for a later date when its sale would be more profitable. Shamrock and Lone Star worked together to obtain the funds to design and build the facility, and on January 1, 1940, the plant began operation, with 6,000 barrels of motor fuel stripped from the processed gas the first day. This led to the advent of liquefied petroleum gas as a major product of Shamrock, and Dunn was instrumental in constructing the first LPG pipelines from the Panhandle field to other regions of Texas and the nation in association with the Phillips Petroleum Company. In 1945 Dunn was made president of the Shamrock Corporation, which by the 1960s emerged as one of the nation's most prosperous petroleum firms. At that time it was merged with the Diamond Alkali Company of Cleveland, Ohio, to form Diamond Shamrock, Incorporated. Dunn was elected chairman of the board of directors in 1960 and served as chairman of the executive committee. He was a member of the Independent National Gas Association of America, the Independent Petroleum Association of America, the Texas Mid-Continent Oil and Gas Association, and the Natural Gas Association, which he served as president from 1945 to 1954.
Dunn was an elder at the First Presbyterian Church in Amarillo, a Mason, and a member of the Khiva Shrine Temple. He served on the boards of the Amarillo Chamber of Commerce, the Tri-State Fair, and the YMCA, where he was president in 1955. He chaired the city's United Fund-Community Chest in 1950 and received the first Amarillo Globe News Annual Community Service Award that year. He also supported the Panhandle-Plains Historical Society and was its president in 1955–56. As an A&M alumnus he was on the Texas A&M Research League, was president of the Amarillo chapter of the Association of Former Students of Texas A&M, and from 1953 to 1959 was on his alma mater's board of regents. In 1972 a new dormitory at Texas A&M was named for him. He was named to the First National Bank of Amarillo board of directions in 1977.
Dunn's association with Cal Farley's Boys Ranch began almost from its inception. He eagerly participated in its fund-raising campaigns and served on the board of directors from 1940 until his death. He supervised the construction of its first water tower and, with Phillips Petroleum and the Fulton construction firm, built the gas pipeline to the ranch facilities. He considered his work for Boys Ranch "the best investment in America," and in 1984 he donated his old hamburger stand from college days to the institution. He died in Amarillo on March 15, 1987, and was interred in Restland Cemetery in Dallas.