Jepson was born at Little Oak Ranch near
Vacaville, California. He became interested in
botany as a boy and explored the adjacent
San Francisco Bay Area, coming into contact with various botanists before he entered college. In 1892, at the age of 25, Jepson,
John Muir, and
Warren Olney formed the
Sierra Club, in Olney's San Francisco law office. From 1895 to 1898, Jepson served as instructor in Botany and carried on research at the
University of California, Berkeley,
Cornell University (1895), and
Harvard University (1896–1897). He received his Ph.D. at Berkeley in 1899. He also created the botanical journal
Erythea, of which he was the editor from 1893 to 1922. He was made assistant professor in 1899, associate professor in 1911, professor in 1918, and professor emeritus in 1937. He was a professor of botany at UC Berkeley for four decades, thus his entire career was identified with the University of California. Jepson founded the
California Botanical Society and served as its president from 1913 to 1915; he also worked as councilor of the
Rancho Santa Ana Botanic Garden. == Legacy ==