Mark Twain's writings had a profound impact on American literature, particularly through his use of regionalism and social criticism. Works such as "The Adventures of Huckleberry Finn" challenged societal norms and addressed issues like race, identity, and morality. Twain's unique narrative style and incorporation of vernacular speech made literature more accessible and relatable, reshaping how stories were told. His emphasis on honesty, humor, and complex character development also influenced future writers to explore deep social themes, ensuring his place as a pivotal figure in literary history.