[2] In 1896, Charles Clark married Katherine Quinn Roberts, who died in New York City in January 1904.
[6] A fan and participant in equestrian sports, Clark resided at his "El Palomar" estate in San Mateo, California, a property he purchased in 1902 which had a polo field and race track.
[1] The owner of Thoroughbred racehorses, among his successful runners was United Verde, a horse named for his mining company.
[7][8] According to Pulitzer winner Bill Dedman, Clark had "the longest private railcar ever built, which he sold to Howard Hughes.
In 1917, the Book Club of California presented an exhibition of 66 incunabula from his collection at the Hill Tolerton Gallery, San Francisco.