The collections of the Library of Congress include more than 32 million cataloged books and other print materials in 470 languages; more than 61 million manuscripts; the largest rare book collection in North America, including the rough draft of the Declaration of Independence, a Gutenberg Bible (one of only three perfect vellum copies known to exist); over 1 million US government publications; 1 million issues of world newspapers spanning the past three centuries; 33,000 bound newspaper volumes; 500,000 microfilm reels; over 6,000 titles in all, totaling more than 120,000 issues comic book titles; films; 5.3 million maps; 6 million works of sheet music; 3 million sound recordings; more than 14.7 million prints and photographic images including fine and popular art pieces and architectural drawings; the Betts Stradivarius; and the Cassavetti Stradivarius.
The Library developed a system of book classification called Library of Congress Classification (LCC), which is used by most US research and university libraries.
The Library serves as a legal repository for copyright protection and copyright registration, and as the base for the United States Copyright Office. Regardless of whether they register their copyright, all publishers are required to submit two complete copies of their published works to the Library—this requirement is known as mandatory deposit. Nearly 22,000 new items published in the U.S. arrive every business day at the Library. Contrary to popular belief, however, the Library does not retain all of these works in its permanent collection, although it does add an average of 10,000 items per day. Rejected items are used in trades with other libraries around the world, distributed to federal agencies, or donated to schools, communities, and other organizations within the United States. As is true of many similar libraries, the Library of Congress retains copies of every publication in the English language that is deemed significant.
The Library of Congress states that its collection fills about 838 miles (1,349 km) of bookshelves, while the British Library reports about 388 miles (624 km) of shelves. The Library of Congress holds more than 155.3 million items with more than 35 million books and other print materials, against approximately 150 million items with 25 million books for the British Library. A 2000 study by information scientists Peter Lyman and Hal Varian suggested that the amount of uncompressed textual data represented by the 26 million books then in the collection was 10 terabytes.
The Library makes millions of digital objects, comprising tens of petabytes, available at its American Memory site. American Memory is a source for public domain image resources, as well as audio, video, and archived Web content. Nearly all of the lists of holdings, the catalogs of the library, can be consulted directly on its web site. Librarians all over the world consult these catalogs, through the Web or through other media better suited to their needs, when they need to catalog for their collection a book published in the United States. They use the Library of Congress Control Number to make sure of the exact identity of the book.
The Library of Congress also provides an online archive of the proceedings of the U.S. Congress at THOMAS, including bill text, Congressional Record text, bill summary and status, the Congressional Record Index, and the United States Constitution.
The Library also administers the National Library Service for the Blind and Physically Handicapped, an audio book and braille library program provided to more than 766,000 Americans.