While the strength of the James S. Copley Library is its choice collection of Americana documents, his role as newspaper publisher and philanthropist undoubtedly spurred him to broaden his collection. His fine press book collection shows a full appreciation for quality printing. American and English literary luminaries span three centuries and include letters by Charlotte Brontë, Charles Dickens, Emily Dickinson, John Steinbeck, Henry David Thoreau, and Walt Whitman, among others. But the real gem is the Mark Twain collection which includes scores of letters written from Twain's time was a cub reporter in San Francisco to end of his life. The letters to his family, friends, and publishers reveal Twain in various moods from playful to cantankerous. The manuscripts include the still unpublished "Family Sketch," begun as a memorial to Twain's favorite daughter Susy, also features candid glimpses into Twain's boyhood and family life.
James S. Copley's philanthropies financed the building of numerous cultural and scientific venues in San Diego. Consequently, the collection contains the autographs of numerous inventors and scientists. There is a rich trove of letters by Marie Curie, Albert Einstein, Thomas Alva Edison, Robert Fulton, Edward Jenner, Isaac Newton, Louis Pasteur and others. American artists are well represented in letters, manuscripts, and publications by Ansel Adams, John James Audubon, Georgia O'Keeffe, Rembrandt Peale, Charles M. Russell. In a letter to his sister, John Singer Sargent describes work on one of his famous plein air paintings. Combining art with literature are dozens of striking literary portraits to which each subject has written a sentiment or a quote from one of his or her works. F. Scott Fitzgerald quotes the last lines of The Great Gatsby. Musicians receive full play as well. Louis Armstrong promises to donate one of his trumpets to a new museum. Duke Ellington eulogizes his pianist and collaborator, Billy Strayhorn. There are also autograph musical quotations by Gershwin, Sousa, and Tchaikovsky.