Richard B. Dillehunt was born in Decatur Illinois on July 12, 1886 to Gussie and Ben Dillehunt. He attended the University of Illinois and matriculated in medicine at the University of Chicago in 1905, graduating in 1910. He interned at the Cook County Hospital. In January of 1912, Dillehunt began his career at the University of Oregon Medical School, on Lovejoy Street, as professor of anatomy. By July 1912, Dean Kenneth Mackenzie appointed him as assistant dean. In this capacity, he kept the school records, wrote the minutes of faculty meetings, approved student admissions, arranged class schedules, and carried the weight of budgetary concerns.

In addition to his clerical duties, he lectured and demonstrated in anatomy and dissection until his resignation as professor in 1917. Noteworthy achievements are a segregation of various laboratory branches into separate departments with full time instructors and standardization of the curriculum. He was an extraordinary assistant to Mackenzie as land was acquired on Marquam Hill for the new site of the medical school. Multnomah County Hospital, Doernbecher Memorial Hospital for Children, the Veteran's Administration Hospital, and the Outpatient Clinic were renowned as a part of "Mackenzie's Dream" but the growth of the medical school can also be attributed to the dedication of Richard B. Dillehunt, his successor and aide.

On March 30, 1920, Dillehunt was elected dean of the school at the same time as his appointment as Clinical Professor of Surgery and head of the department of Orthopedic Surgery. He was well known for advancements in surgery and his contributions to orthopedic surgery. He was a member of various societies including Alpha Omega Alpha, Phi Rho Sigma, Oregon and Multnomah County Medical Societies, North Pacific Surgical Association, Pacific Northwest Medical Association, Pacific Coast Surgical Association, American Academy of Orthopedic Surgeons, American Orthopedic Association, North Pacific Orthopedic Society, Oregon Mental Hygiene Society, Board of Directors of the Oregon Tuberculosis Association and the American College of Surgeons. In 1935 President Roosevelt appointed him to the Advisory Committee of Orthopedic Surgeons. He was chief of the orthopedic staff at Doernbecher Memorial Hospital for Children from 1926-1943 and a member of the surgical staffs of Emanuel and Multnomah County Hospitals. He was chief surgeon at Shriner's Hospital for Crippled Children where he was well known for his warmth, sympathy and skill. Dr. Dillehunt was dedicated to civic and philanthropic movements. He dedicated himself not only to the medical school but served in WWI. He helped organize a base hospital and went with it to France as head of orthopedic surgery. He began his service as 1st lieutenant in the medical corps and returned to Portland in 1912 as a Major. Dr. Dillehunt died at his home in 1953.