Because Mark Twain has made great contributions to American literature.

Mark Twain's contribution to the development of realism and to American literature as a whole was partly through his theories of localism in American fiction, and partly through his colloquial style.

Mark Twain preferred to represent social life through portraits of local places which he knew best. Indeed, he started off as a teller of tall tales and local colorist. He felt that a novelist must not try to generalize about a nation.

One of Mark Twain' significant contributions to American literature lies in the fact that he made colloquial speech an accepted, respectable literary medium in the literary history of the country. The style has impacted American literature and made books before Huck Finn and after it quite different. Its influence is clearly visible in twentieth-century American literature. It is continued in both prose and poetry. Sherwood Anderson took his cue from Mark Twain and became about the first writer after Twain to take the vernacular as a serious way of presenting reality. Anderson was for a while Hemingway's mentor in the colloquial style. Ernest Hemingway was the direct descendant of Mark Twain.