Within the framework of this article, the Public Library is considered as one of the main centers of historical science of Petrograd/Leningrad of the early Soviet period. Based on a complex of published and archival sources and the processing of an extensive database of biographical data, the collective portrait of historians who worked in the Public Library in 1917-1934 was reconstructed. The article analyzes various data associated with their scientific biography. The problems of mobility / turnover of personnel among historians-librarians are considered, it is shown in which institutions they most often worked part-time. The article analyzes the processes of restructuring the work of the Public Library in new socio-political conditions and reveals the attitude of historians to these changes. There is an evidential opinion that the historians of the Public Library, even though they found themselves after 1917 in a hostile social and political environment, were able to preserve the possibility of working outside the ideological control of the Soviet state for a long time. Only the restructuring of the entire structure and structure of the library in the second half of the 1920s and early 1930s led to the outflow or expulsion of many professional historians from the Public Library.