Chester G. Gillespie was the first chief of the Bureau of Sanitary Engineering in the State Department of Public Health (1915-1947). He was born and raised in San Benito County, near Hollister and graduated from UC Berkeley in 1907 as a Sanitary Engineer. One of Gillespie’s major accomplishments was the suit by the State Department of Public Health against the City of Los Angeles. He also oversaw the water and sewage treatment facilities at Golden Gate Park, Folsom Prison and Big Basin. In this interview Gillespie discusses early water supply systems in the Bay Area, research and consultation in water purification and sewage treatment, the Santa Fe typhoid epidemic (1924), the Sacramento water filtration plant and Wilfred F. Langelier who was the Professor of Sanitary Engineering at UC Berkeley. This interview is part of a group of interviews documenting sanitary engineering in California.