Leo Wiener was a historian and linguist of Polish-Jewish origin and was professor of Slavic literatures at Harvard in the early 20th century. This paper presents an overview of the history, culture, and language of the Jews who emigrated from Germany to Slavic countries and continued to speak a dialect of German. This survey of Jewish language within Russia before the 1903-1906 pogroms (not to mention the Holocaust) make this a valuable documentation of Jewish culture in Europe.