Native American literature is literature, both oral and written, produced by Native Americans in what is now the United States (as distinct from First Nations writers in Canada), from pre-Columbian times through to today. Famous authors include N. Scott Momaday, Leslie Marmon Silko, Simon Ortiz, Louise Erdrich, Gerald Vizenor, Joy Harjo, Sherman Alexie, D'Arcy McNickle, James Welch, Charles Eastman, Mourning Dove, Zitkala-Sa, John Rollin Ridge, Lynn Riggs, Hanay Geiogamah, William Apess, Samson Occom, and Stephen Graham Jones. Importantly, it is not "a" literature, but a set of literatures, since every tribe has its own cultural traditions. Since the 1960s, it has also become a significant field of literary studies, with academic journals, departments, and conferences devoted to the subject.