Clark, William Andrews, Jr., 1877-1934

In 1902, he married Mabel Duffield Foster (1881-1903), who had grown up in Butte just down the street from the Clark residence. Mabel died of sepsis following the birth of their son, William Andrews Clark, III ("Tertius"), in 1903. In 1907, Clark married Alice Genevieve McManus Medin (1884-1918), a recent divorcee originally from Virginia City, Nevada, and they moved from Butte to Los Angeles in the early 1910s. Their house at Adams Boulevard and Cimarron Street occupied the grounds that the Clark Library still stands on today. Though Clark would continue to be involved in the Elm Orlu Mine and Timber Butter Milling Company, among other mining businesses until his death, he does not appear to have worked actively as a lawyer after his move to Los Angeles. Alice McManus Clark died at the Clark residence in Los Angeles in November 1918. Clark never remarried, and soon after Alice's death, met his long-time partner, Harrison Post.

Around the time of his move to LA, WAC Jr. began collecting antiquarian and fine press books as a serious hobby (he had dabbled in book buying previous to this). In 1919, he hired bibliographer Robert E. Cowan to consult on collection-building and the compilation of a printed library catalog. The first volume of this was printed in 1920 by San Francisco printer John Henry Nash, and many other volumes, dedicated to different portions of the collection, would be issued over time, all printed by Nash.

After a small kitchen fire in his home around 1924, Clark decided he needed a separate, fireproof library building and hired architect Robert David Farquhar to design the present library building, with interior decoration by Harrison Post. Upon completion in 1926, Clark promised the library and grounds to UCLA after his death. When Clark died in Montana in 1934, the Clark Library became a part of UCLA.