Paine grew up in Iowa and Illinois, leaving school at fifteen. At twenty he went to St. Louis, where he worked as a photographer; several years later he operated a photographic supply business in Kansas. After one of his stories was accepted by Harper’s Weekly, he moved to New York in 1895, where he wrote for periodicals and published books for both children and adults. In 1899 he became an editor of the St. Nicholas Magazine for young people, and in 1904 published Th. Nast: His Period and His Pictures, the first of his many biographies. Paine approached SLC about writing his biography, and in January 1906 SLC installed him as a member of the household. As SLC’s literary executor, Paine closely controlled access to the unpublished papers. His Mark Twain: A Biography appeared in 1912, and was followed by editions of the Letters (1917), Autobiography (1924) and Notebook (1935). He also prepared (and drastically rewrote) the first edition of The Mysterious Stranger (1916). Paine’s unparalleled access to SLC in his last years, and to his private papers, give him a continuing place in Mark Twain studies, made somewhat controversial by his zeal to protect the image of the author.