Mark Twain made significant contributions to American literature and culture with works like "The Adventures of Tom Sawyer" and "Adventures of Huckleberry Finn". He is celebrated for his mastery of realism and social commentary, addressing issues like race and morality with humor and insight. Twain's unique narrative voice and use of vernacular speech brought authenticity to American storytelling, influencing subsequent generations of writers. His legacy continues in literature and discussions of American identity and societal values.