The Petaluma Historic Library and Museum's Research Library, named after Petaluma City Historian Hoppy Hopkins (1921-2003), contains books and files that assist in history, genealogy, and architectural research of Petaluma and close environs. Collection strengths include such treasures as: early maps, the Vallejo land grant; books relating to topics as the Miwok Indians, poultry and dairy industries; histories of surrounding communities; blueprints of homes and buildings designed by local architect Brainerd Jones; city directories from as early as 1875; yearbooks from the 1890s; and a copy of the first newspaper published in Petaluma in August of 1855.
The Petaluma Historic Library and Museum's digital collection at California Revealed consists of texts, moving images, and audio recordings from the 1920s to 2010s. The collection includes many oral histories, interviews, and home movies related to topics such as Petaluma Chicken Ranches, genealogy, the Argus Courier Newspaper, the Bojorques family, and the Petaluma Museum.