Douglas Gunn was born 1841 in Ohio to Dr. and Mrs. Lewis C. Gunn. His family moved to Sonora, California 1852, where his father bought and ran the Sonora Herald. In 1860 his family moved to San Francisco, California where his father edited the Times, then they moved again in 1868 to San Diego. During this time Douglas Gunn learned the newspaper trade, working for San Diego Union. He lived in New Town San Diego and walked daily to Old Town, where the paper was published. In 1871 he bought the paper, moved it to New Town, and made it a daily paper. Gunn ran the paper until about 1886.
Gunn was mayor of San Diego from 1889 until 1891. He was the first mayor to serve after a new city charter, with a mayoral form of government replaced a Board of Trustees that served from 1852 to 1889. Although a Republican, the party ran two separate tickets in the mayoral election, with Gunn on the "Citizens' Non-Partisan" ticket.
Gunn's civic works include establihing a metropolitan police department for San Diego, having the Santa Fe Railroad build tracks to San Diego, organizing a company of the National Guard, and publishing an illustrated history of the county, Picturesque San Diego (1887).