James Madison is credited with the idea of creating a congressional library, first making such a proposition in 1783.

The Library of Congress was subsequently established April 24, 1800 when President John Adams signed an act of Congress providing for the transfer of the seat of government from Philadelphia to the new capital city of Washington. Part of the legislation appropriated $5,000 "for the purchase of such books as may be necessary for the use of Congress ... and for fitting up a suitable apartment for containing them". Books were ordered from London, and the collection consisted of 740 books and three maps which were housed in the new United States Capitol.

President Thomas Jefferson played an important role in establishing the structure of the Library of Congress. On January 26, 1802, he signed a bill that allowed the president to appoint the librarian of Congress and establishing a Joint Committee on the Library to regulate and oversee it. The new law also extended borrowing privileges to the president and vice president.

The invading British army burned Washington in August 1814 during the War of 1812 and destroyed the Library of Congress and its collection of 3,000 volumes.These volumes had been left in the Senate wing of the Capitol.

Within a month, Thomas Jefferson offered to sell his personal library as a replacement. Congress accepted his offer in January 1815, appropriating $23,950 to purchase his 6,487 books.

On December 24, 1851, the largest fire in the library's history destroyed 35,000 books, about two–thirds of the library's collection and two-thirds of Jefferson's original transfer.

Congress appropriated $168,700 to replace the lost books in 1852 but not to acquire new materials. This marked the start of a conservative period in the library's administration by librarian John Silva Meehan and joint committee chairman James A. Pearce, who restricted the library's activities. Meehan and Pearce's views about a restricted scope for the Library of Congress reflected those shared by members of Congress. While Meehan was librarian he supported and perpetuated the notion that "the congressional library should play a limited role on the national scene and that its collections, by and large, should emphasize American materials of obvious use to the U.S. Congress".

During the 1850s, Smithsonian Institution librarian Charles Coffin Jewett aggressively tried to make the Smithsonian into the United States' national library. His efforts were blocked by Smithsonian secretary Joseph Henry, who advocated a focus on scientific research and publication. To reinforce his intentions for the Smithsonian, Henry established laboratories, developed a robust physical sciences library and started the Smithsonian Contributions to Knowledge, the first of many publications intended to disseminate research results.

For Henry, the Library of Congress was the obvious choice as the national library. Unable to resolve the conflict, Henry dismissed Jewett in July 1854.

In 1859, Congress transferred the library's public document distribution activities to the Department of the Interior and its international book exchange program to the Department of State.

Abraham Lincoln appointed John G. Stephenson as librarian of Congress in 1861 and the appointment is regarded as the most political to date. Stephenson was a physician and spent equal time serving as librarian and as a physician in the Union Army. He could manage this division of interest because he hired Ainsworth Rand Spofford as his assistant.

In 1865 the Smithsonian building, also called the Castle due to its Norman architectural style, was devastated by fire and presented Henry an opportunity in regards to the Smithsonian's non-scientific library. Around this time, the Library of Congress was making plans to build and relocate to the new Thomas Jefferson Building, which would be fire proof.

The Library of Congress reasserted itself during the latter half of the 19th century under Librarian Ainsworth Rand Spofford who directed it from 1865 to 1897. He built broad bipartisan support for it as a national library and a legislative resource, aided by an overall expansion of the federal government and a favorable political climate. He began comprehensively collecting Americana and American literature, led the construction of a new building to house the library, and transformed the librarian of Congress position into one of strength and independence.

Authorized by an act of Congress, Joseph Henry transferred the Smithsonian's non-scientific library of 40,000 volumes to the Library of Congress in 1866.

By 1876, the Library of Congress had 300,000 volumes and was tied with the Boston Public Library as the nation's largest library.

A year before the library's move to its new location, the Joint Library Committee held a session of hearings to assess the condition of the library and plan for its future growth and possible reorganization. Spofford and six experts sent by the American Library Association testified that the library should continue its expansion towards becoming a true national library. Congress more than doubled the library's staff from 42 to 108 based on the hearings, and with the assistance of senators Justin Morrill of Vermont and Daniel W. Voorhees of Indiana, and established new administrative units for all aspects of the collection. Congress also strengthened the office of Librarian of Congress to govern the library and make staff appointments, as well as requiring Senate approval for presidential appointees to the position.

It moved from the Capitol building to its new headquarters in 1897 with more than 840,000 volumes, 40 percent of which had been acquired through copyright deposit.

The Library of Congress, spurred by the 1897 reorganization, began to grow and develop more rapidly. Spofford's successor John Russell Young, though only in office for two years, overhauled the library's bureaucracy, used his connections as a former diplomat to acquire more materials from around the world, and established the library's first assistance programs for the blind and physically disabled.

Young's successor Herbert Putnam held the office for forty years from 1899 to 1939.

Young's successor Herbert Putnam held the office for forty years from 1899 to 1939, entering into the position two years before the library became the first in the United States to hold one million volumes.

Putnam's tenure also saw increasing diversity in the library's acquisitions. In 1903, he persuaded President Theodore Roosevelt to transfer by executive order the papers of the Founding Fathers from the State Department to the Library of Congress.

Putnam expanded foreign acquisitions as well, including the 1904 purchase of a four-thousand volume library of Indica.

The 1906 purchase of G. V. Yudin's eighty-thousand volume Russian library.

The 1908 Schatz collection of early opera librettos.

In 1914, Putnam established the Legislative Reference Service as a separative administrative unit of the library. Based in the Progressive era's philosophy of science as a problem-solver, and modeled after successful research branches of state legislatures, the LRS would provide informed answers to Congressional research inquiries on almost any topic.

Collections of Hebraica and Chinese and Japanese works were also acquired. Congress even took the initiative to acquire materials for the library in one occasion, when in 1929 Congressman Ross Collins of Mississippi successfully proposed the $1.5 million purchase of Otto Vollbehr's collection of incunabula, including one of three remaining perfect vellum copies of the Gutenberg Bible.

The early 1930s purchase of the Russian Imperial Collection, consisting of 2,600 volumes from the library of the Romanov family on a variety of topics.

Congress acquired nearby land in 1928 and approved construction of the Annex Building (later the John Adams Building) in 1930. Although delayed during the Depression years, it was completed in 1938 and opened to the public in 1939.

Putnam retired in 1939.

President Franklin D. Roosevelt appointed Archibald MacLeish as his successor. Occupying the post from 1939 to 1944 during the height of World War II. MacLeish became the most visible librarian of Congress in the library's history. MacLeish encouraged librarians to oppose totalitarianism on behalf of democracy; dedicated the South Reading Room of the Adams Building to Thomas Jefferson, commissioning artist Ezra Winter to paint four themed murals for the room; and established a "democracy alcove" in the Main Reading Room of the Jefferson Building for important documents such as the Declaration, Constitution and The Federalist Papers.

MacLeish resigned in 1944 to become Assistant Secretary of State.

President Harry Truman appointed Luther H. Evans as librarian of Congress. Evans, who served until 1953, expanded the library's acquisitions, cataloging and bibliographic services as much as the fiscal-minded Congress would allow, but his primary achievement was the creation of Library of Congress Missions around the world.

Evans' successor Lawrence Quincy Mumford took over in 1953. Mumford's tenure, lasting until 1974, saw the initiation of the construction of the James Madison Memorial Building, the third Library of Congress building. Mumford directed the library during a period of increased educational spending, the windfall of which allowed the library to devote energies towards establishing new acquisition centers abroad, including in Cairo and New Delhi.

A 1962 memorandum by Douglas Bryant of the Harvard University Library, compiled at the request of Joint Library Committee chairman Claiborne Pell, proposed a number of institutional reforms, including expansion of national activities and services and various organizational changes, all of which would shift the library more towards its national role over its legislative role. Bryant even suggested possibly changing the name of the Library of Congress, which was rebuked by Mumford as "unspeakable violence to tradition".

In 1965, Congress passed an act allowing the Library of Congress to establish a trust fund board to accept donations and endowments, giving the library a role as a patron of the arts. The library received the donations and endowments of prominent individuals such as John D. Rockefeller, James B. Wilbur and Archer M. Huntington.

In 1967, the library began experimenting with book preservation techniques through a Preservation Office, which grew to become the largest library research and conservation effort in the United States. Mumford's administration also saw the last major public debate about the Library of Congress' role as both a legislative library and a national library.

Debate continued within the library community until the Legislative Reorganization Act of 1970 shifted the library back towards its legislative roles, placing greater focus on research for Congress and congressional committees and renaming the Legislative Reference Service to the Congressional Research Service.

Mumford retired in 1974.

Gerald Ford appointed Daniel J. Boorstin as librarian.

Boorstin's active and prolific role changed the post of librarian of Congress so that by the time he retired in 1987, The New York Times called it "perhaps the leading intellectual public position in the nation".

President Ronald Reagan nominated James H. Billington as the 13th librarian of Congress in 1987, and the U.S. Senate unanimously confirmed the appointment.

In 1988, The library also established the National Film Preservation Board, a congressionally mandated National Film Preservation Board to select American films annually for preservation and inclusion in the new National Registry, a collection of American films the library has made available on the Internet for free streaming.

American Memory created in 1990, which became The National Digital Library in 1994, providing free access online to digitized American history and culture resources with curatorial explanations for K-12 education.

Billington established the Library Collections Security Oversight Committee in 1992 to improve protection of collections, and also the Library of Congress Congressional Caucus in 2008 to draw attention to the library's curators and collections.

Thomas.gov website launched in 1994 to provide free public access to U.S. federal legislative information with ongoing updates.

During Billington's tenure as the 13th librarian of Congress, the library acquired Lafayette's previously inaccessible papers in 1996 from a castle at La Grange, France.

The National Book Festival, founded in 2000 with Laura Bush, has brought more than 1000 authors and a million guests to the National Mall and the Washington Convention Center to celebrate reading. With a major gift from David Rubenstein in 2013, the library also established the Library of Congress Literacy Awards to recognize and support achievements in improving literacy in the U.S. and abroad.

The library also launched the Living Legend Awards in 2000 to honor artists, activists, filmmakers, and others who have contributed to America's diverse cultural, scientific, and social heritage.

The Kluge Center, started with a grant of $60 million from John W. Kluge in 2000 to bring scholars and researchers from around the world to use library resources and to interact with policymakers and the public. It hosts public lectures and scholarly events, provides endowed Kluge fellowships, and awards The Kluge Prize for the Study of Humanity, the first Nobel-level international prize for lifetime achievement in the humanities and social sciences (subjects not included in the Nobel awards).

Open World Leadership Center, established in 2000, administered 23,000 professional exchanges for emerging post-Soviet leaders in Russia, Ukraine, and the other successor states of the former USSR by 2015. Open World began as a Library of Congress project, and later became an independent agency in the legislative branch.

The Veterans History Project, congressionally mandated in 2000 to collect, preserve, and make accessible the personal accounts of American war veterans from WWI to the present day.

Under Billington, the library launched a mass deacidification program in 2001, which has extended the lifespan of almost 4 million volumes and 12 million manuscript sheets; and new collection storage modules at Fort Meade, the first opening in 2002, to preserve and make accessible more than 4 million items from the library's analog collections.

The library acquired the only copy of the 1507 Waldseemüller world map ("America's birth certificate") in 2003 for permanent display in the library's Thomas Jefferson Building.

The National Audio-Visual Conservation Center, which opened in 2007 at a 45-acre site in Culpeper, Virginia with the largest private gift ever made to the library (more than $150 million by the Packard Humanities Institute) and $82.1 million additional support from Congress.

The Gershwin Prize for Popular Song, launched in 2007 to honor the work of an artist whose career reflects lifetime achievement in song composition. Winners have included Paul Simon, Stevie Wonder, Paul McCartney, Burt Bacharach and Hal David, Carole King, Billy Joel, and just-named Willie Nelson for November 2015.

By 2008, the librarians of Congress had found replacements for all but 300 of the works that were in Jefferson's original collection.

The Fiction Prize (now the Library of Congress Prize for American Fiction) started in 2008 to recognize distinguished lifetime achievement in the writing of fiction.

Using privately raised funds, the Library of Congress reconstructed Thomas Jefferson's original library, which was placed on permanent display in the Jefferson building in 2008.

The World Digital Library, established in association with UNESCO and 181 partners in 81 countries in 2009, to make online copies of professionally curated primary materials of the world's varied cultures freely available in multiple languages.

National Jukebox launched in 2011 to provide streaming free online access to more than 10,000 out-of-print music and spoken word recordings.

Congress.gov website to provide a state-of-the-art framework for both Congress and the public in 2012.

BARD in 2013, digital talking books mobile app for Braille and Audio Reading Downloads in partnership with the library's National Library Service for the blind and physically handicapped, that enables free downloads of audio and Braille books to mobile devices via the Apple App Store.

Under Billington's leadership, the library doubled the size of its analog collections from 85.5 million items in 1987 to more than 160 million items in 2014.

Before retiring in 2015, after 28 years of service, Billington had come "under pressure" as librarian of Congress. This followed a Government Accountability Office report which revealed a "work environment lacking central oversight" and faulted Billington for "ignoring repeated calls to hire a chief information officer, as required by law".

When Billington announced his plans to retire in 2015, commentator George Weigel described the Library of Congress as "one of the last refuges in Washington of serious bipartisanship and calm, considered conversation," and "one of the world's greatest cultural centers".

Carla Hayden was sworn in as the 14th librarian of Congress on September 14, 2016, becoming both the first woman and the first African-American to hold the position.

In 2017, the library announced the Librarian-in-Residence program which aims to support the future generation of librarians by giving them opportunity to gain work experience in five different areas of librarianship including: Acquisitions/Collection Development, Cataloging/Metadata, and Collection Preservation.