The Rare Book Division's holdings of materials of interest to Polish specialists are extensive and diverse. Janina Hoskins' 1973 work Early and Rare Polonica in American Libraries indicates 270 titles among the Library of Congress holdings dating from the 15th-17th centuries; 121 of these works were found in no other American repository. The Rare Book Division also possesses a rich collection of 18th-20th- century Polonica. Many of these works are to be found in the numerous special collections in the custody of the Rare Book Division, including the well-known Jefferson, Yudin, Russian Imperial, and Rosenwald collections.
The Rare Book Division has a special collection of miniature editions of literary works, including several dozen by Polish writers. Reflecting the composition of the Library's general Polish collection, the largest share of the Rare Book Division's Polonica falls under the heading of history, followed by belles lettres, the physical sciences, and religion. Subject classification of these older works, however, obscures their intrinsic interest to researchers across disciplines. Notable examples of the Library's rare Polonica include the titles listed below which link to fuller bibliographic information in the Library of Congress Online Catalog.
The unique materials of the Rare Book and Special Collections Division, now totaling over 1 million items, include books, broadsides, pamphlets, theater playbills, prints, posters, photographs, and medieval and Renaissance manuscripts. At the center is Thomas Jefferson's book collection, which was sold to Congress in 1815. The Rare Book & Special Collections Reading Room is modeled after Philadelphia's Independence Hall. This room is home to the divisional catalogs, reference collection, and reference staff. Collections are stored in temperature and humidity controlled vaults.