Brief Description: Correspondence with several thousand individuals, 1907-1961, including S. An-Ski, Shalom Asch, David Bergelson, Nathan Birnbaum, Menahem Boraisha, Ber Borochov, Marc Chagall, Jacob Dinesohn, Simon Dubnow, Aaron Glanz- Leieles, Jacob Glatstein, Chaim Grade, Reuben Iceland, Leon Kobrin, Louis Lamed, Leibush Lehrer, H. Leivick, Jacob Lestschinsky, Abraham Liessin, Joseph Opatoshu, Isaac Leib Peretz, David Pinsky, Alexander Pomerantz, Moshe Starkman, Isaac Nachman Steinberg, Abraham Sutzkever, Max Weinreich, Chaim Zhitlowsky. Family correspondence, 1909-1960, with Niger's mother, wife, children, brothers Daniel Charney and Baruch Vladeck, other relatives. Letters from readers of Niger's columns. Correspondence with hundreds of organizations including Yiddish periodicals, publishing houses, educational and cultural institutions, professional associations, especially institutions he was closely involved with such as the YIVO, Congress for Jewish Culture, Louis Lamed Fund, *The Day*, I. L. Peretz Yiddish Writers' Union, *Zukunft*. Manuscripts and typescripts of major works by Niger on Isaac Leib Peretz, Shalom Asch, H. Leivick, Isaac Meir Dick. Bibliographical materials on various topics in Yiddish literature. Speeches and lectures. Manuscripts of other writers, including Salo Baron, Daniel Charney, Philip Friedman, Szmerke Kaczerginski, Yona Rosenfeld, Abraham Reisen. Clippings of Niger's regular columns published in *The Day* (*Der tog*), *Day-Morning Journal* (*Der tog-morgn zhurnal*), *Di yidishe velt*. Niger's aricles pertaining to other writers, or on topics of Jewish interest, such as Jewish education, Yiddish literature, Zionism, religious issues, the Holocaust, Niger's travels. Clippings by other writers about Niger. Biographical materials about Niger, 1907-1957. Manuscripts and notebooks of Niger's diary. Materials on Niger's activities in Russia during World War I, and his immigration to the U.S. Personal documents such as passports, invitations, including invitation to the Czernowitz Conference on Yiddish, 1908. Materials relating to copyright. Obituaries.