Thirteen U.S. citizens have won the Nobel Prize in Literature. William Faulkner, Ernest Hemingway and John Steinbeck are often named among the most influential writers of the 20th century. Popular literary genres such as the Western and hardboiled crime fiction developed in the United States. The Beat Generation writers opened up new literary approaches, as have postmodernist authors such as John Barth, Thomas Pynchon, and Don DeLillo.