There are examined the underexplored libraries of the provincial scientific archival commissions at the example of Kostroma and Vladimir provinces. Appeared in the 1880-ies in the Upper Volga region, these research organizations — provincial scientific archival commissions (GUAC) — had significantly enriched the local book culture and contributed to the further development of librarianship in the region. The local intelligentsia, standing at the origins of the first scientific libraries in the Upper Volga Region, joined around these commissions. Thanks to the work of GUAC there had survived a great number of written historical sources. Such libraries had saved from destruction significant amount of literary monuments on the territory of the Upper Volga region, including unique manuscripts and early printed books, and had preserved historical and scientific publications. There is described the library and educational activities of Kostroma GUAC, started its work in 1885. There is revealed contribution of Vladimir GUAC, which operated since 1898, to the development of librarianship of the Upper Volga region. On the basis of the published works of commissions and archival materials there is shown the role of these libraries on preservation of the book monuments, valuable scientific editions and documents on the history of Kostroma and Vladimir land. Some of the materials from the libraries of Kostroma and Vladimir provincial scientific archival commissions nowadays are preserved in the collections of the State Archives of Kostroma and Vladimir regions.