Leonard Winfield Larson was born on May 22, 1898, to John and Ida (Anderson) Larson, in Clarkfield, Minnesota. After attending grade school and high school there, Larson enrolled in St. Olaf Academy in Northfield, Minnesota. In 1918 he graduated with a Bachelor of Science degree from the University of Minnesota, and in 1924 received a Doctor of Medicine degree magna cum laude from the University of Minnesota Medical School.
From medical school, Larson went into general practice at Northwood, Iowa, for six months. He returned to the University of Minnesota for postgraduate work, and in 1924 joined the Quain and Ramstad Clinic in Bismarck, North Dakota, where he became the first practicing pathologist in the state.
During the 1930s he became active in various medical organizations. He was secretary from 1940-1947 and president from 1950-1951 of the North Dakota State Medical Association, and president of the American Society of Clinical Pathologists from 1939-1940. Larson was also involved as the American Cancer Society president from 1965-1966, U.S. Delegate to the World Medical Association 1956-1966, and a member of the U.S. Delegation to the World Health Assemblies in 1952, 1953, 1959, and 1961.
Larson was especially active in the American Medical Association. He served on the House of Delegates from 1939-1950, Board of Trustees 1950-1960, Executive and Finance committee, 1957-1959, Chairman, 1958-1960, Vice President and President-elect, 1960-1961, and President, 1961-1962. The more important committees on which he served were Committee on Blood, chairman, 1948-1959, Correlating Committee on Lay-sponsored Voluntary Health Plans, chairman, 1948-1950, and Commission on Medical Care Plans, chairman, 1955-1959. This committee issued the "Larson Report" which became the basis for the AMA's position on national health care.
In Bismarck, Larson was a member of the school board for nine years and helped to organize Bismarck Junior College. He was a trustee of Jamestown College, which conferred on him an honorary Doctor of Science degree in 1961. His involvement in honorary fraternities included Sigma Xi, Alpha Omega Alpha, and Phi Beta Pi.
Larson married Ordelia Miller on October 23, 1923; they had two daughters, Margery and Dorothy. After Ordelia's death, Larson married Esther D. Knudston on June 29, 1969. Leonard W. Larson died in Bismarck, on September 30, 1974.
The Dr. Leonard W. Larson Papers date from 1948 to 1968 and have been divided into three series:
Series 1: Organizations
Series 2: Personal and Biographical
Series 3: Photographs