The Polish Peasant in Europe and America, a multivolume masterpiece by William Thomas and Florian Znaniecki published between 1918 and 1921, came to defne early American sociology. One of its most important contributions was the in?uential social disorganization paradigm, which distinguished primary-group organization, social disorganization, and social reorganization. This paper contends that nation-building and the civil incorporation of Jews in postwar Poland and the United States were important background conditions for the creation of this social disorganization paradigm. This thesis is supported with a threefold comparison. The Polish Peasant in Europe and America is contrasted toOld World Traits Transplanted, a book published in 1921 and largely written by Thomas, though credited to the American sociologists Robert Park and Herbert Miller. This textual comparison makes possible a further comparison of social reorganization in Polish territory and the United States. Lastly, the essay highlights the contrasts that Thomas and Znaniecki drew between Poles and Jews within each of these national contexts, and the role these contrasts played in the development of the social disorganization paradigm. The paper concludes with some re?ections drawn from The Polish Peasant in Europe and America about why the civil incorporation of outgroups sometimes fails, and how it might succeed.