Robert (Bob) R. Thomsen was born in Wahpeton, North Dakota, in 1914. He received his Bachelor of Science in Education with majors in mathematics and physical education from the University of North Dakota in 1934. Between 1943 and 1946, he served as a Lieutenant in the Navy as an air navigator instructor for Naval Air Station (NAS) Pensacola and NAS Pacific. From the University of Wyoming he earned his Masters of Arts in 1950 and Ph.D. in Education in 1952. Bob Thomsen served as an assistant athletic coach, an athletic coach, and a high school principal for various high schools in Minnesota. He was a football and track coach at the Springfield High School Institute and a graduate assistant in the physical education department, and director of intramurals and supervisor for student cumulative records at the University of Wyoming. He was also active in the Boys Scouts and Little League.

In September 1952, Thomsen came to Whitman College. For 27 years he held both athletic and administrative posts. He was first assistant football coach (succeeding Joe Ponsalle) and from 1955, he was the head football coach (succeeding Joe Beidler). From 1963, he was golf coach and from 1969, cross country coach and chairman of the department of physical education. From 1954 until 1969, he was Dean of Men. He retired from Whitman College in 1979, but he has stayed actively involved with humanitarian organizations and a member of various city councils.

Some of the organizational memberships Thomsen has held during the years are: Alpha Tau Omega, Phi Kappa Phi, Phi Epsilon Kappa, Phi Delta Kappa, National College Physical Education Association for Men, National Association of Intercollegiate Athletics Coaches, American Association for Health, Physical Education and Athletics, American Deans, Walla Walla Bowling Association, Masonic Lodge, El Katif Temple, Blue Mountain Shrine Club (President, 1969), United Fund Campaigner, Rotary International, Walla Walla and Big Blue Booster Clubs, and Chairman of Judges - Juvenile Commission. He was also the recipient of the 18th annual Town-Gown Award in 1978.

In 1940 he married Ruth Elisabeth Finely and had a son, Thomas (Tommy) Finely Thomsen. He also has five grandchildren.