Dovid Katz, who has taught at Oxford, Yale and Vilnius University, and is now an independent researcher based in Vilnius, has released today the 2015 base version of his map of the traditional Litvak culture area in northeastern Europe. Unlike nation-states, Litvaks never had any interest in conquering or controlling anything.
They were happy to be a peaceful minority with its own conceptualization of the world around them, with its own Yiddish language and also Yiddish forms for every place name. This map differs from the dialect map of the dialect the author calls Litvish, because it is based on cultural self-definition, and there are some mixed dialect areas (around Brisk/Brest and around Chernobyl) that could be classified either way, and there is a large "Colonial Litvish" area that stretched all the way to the Black Sea, since the czarist colonizations there of the early 19th century. Some villages even have names like Nay-Kovne, but in general the Jewish communities did not necessarily consider themselves "Litvak."
This map is part of the author's project of a quarter century, based on dozens of expeditions to find and record the last, oldest Yiddish speakers in Lithuania, Belarus, Latvia, Estonia, northeastern Poland and eastern and northern Ukraine (sometimes westernmost Russia, as well). The Atlas is only slowly being cartographed and put on line at: Atlas of Northeastern Yiddish – Sample maps