Question

Realism was a fairly influential and widespread literary movement in the United States in the latter half of the nineteenth century. Which American writer is among the pioneers of American realism?

Answer 1

There are many American writers that are among the pioneers of American realism. 

A few of them are: 
1)Kate Chopin
2)Edith Wharton
3)Willa Carter
4)Mark Twain

Answer 2

Mark Twain is the answer.