Charles S. Greene, poet and former editor of the Overland Monthly, became librarian in 1899 and served until 1926. Mabel W. Thomas, who served as assistant librarian and chief reference librarian under Greene, and retired in 1948, began a collection of books, periodicals, and other material that were the foundation of the California Room in the 1940s and now contained in the well-used Oakland History Room.
Charles S. Greene's tenure as librarian began in 1899 and lasted until 1926. Mabel W. Thomas, who served under Greene as assistant librarian and chief reference librarian, left her position in 1948 and started compiling a collection of books, periodicals, and other materials that would eventually become the foundation of the California Room in the 1940s, which is now part of the Oakland History Room.