Upton Beall Sinclair (September 20, 1878 - November 25, 1968) was a prolific author of nearly 100 books and numerous articles on a variety of subjects, including socialism, health, journalism, and workers’ rights. His most notable works include The Jungle (1906), Oil! (1926), and the multi-volume Lany Budd series (1940 to 1953), the third book of which won the Pulitzer Prize in 1943. He unsuccessfully ran for Governor of California in 1934 on his EPIC (End Poverty in California) campaign, which later influenced aspects of President Franklin D. Roosevelt’s New Deal programs, enacted in the mid-1930s.

Arthur Elmer Belt, M.D. (1893-1980) was a prominent Los Angeles urologist and avid book collector, particularly of works by and about Leonardo Da Vinci, Florence Nightingale, Silas Weir Mitchell, and Upton Sinclair. In addition to running a successful private practice, Dr. Belt was instrumental in the founding of the School of Medicine at the University of California, Los Angeles in 1951 where he subsequently taught as Clinical Professor of Surgery (Urology). He donated his Da Vinci collection to UCLA in 1961.

Willard S. Morse (1856-1935) was a mining executive in the West and Mexico. In 1906, he became director and member of the executive committee of the American Smelter Securities Company, Chilean Exploration Company, and Braden Copper Company. After retiring, Morse devoted much of his time to the collection of Americana books and materials.