At the core of the founding of the Hoover Institution in 1919, the Hoover Institution Library and Archives are a central part of the overall mission of the Institution. By collecting rare and unique material on political, economic, and social change in the modern era; preserving it; and providing it to researchers, the library and archives provide a rich and growing knowledge base and promote and encourage scholarship and research.

Archival holding amount to nearly 6,000 separate collections that encompass an estimated 50 million original documents; 15 million documents on microfilm; upward of 15 million digitized images; more than 100,000 speeches, broadcasts, and historical records on audiotape and videos; and some 120,000 political posters. The library holds 900,000 rare books, special collections, and serials.

Collecting areas of special interest include Nationalist China, imperial Russia, the USSR and post-Soviet Russia and Central and East Europe, political ideologies and movements in the United States and the West, and the broadcast collections of Radio Free Europe/Radio Liberty and Firing Line .