(The Library of Congress building, under construction in 1893.)
According to the web site of the Library itself ("Today in History"), "On April 24, 1800, President John Adams approved the appropriation of $5,000 for the purchase of 'such books as may be necessary for the use of Congress.'
"The books, the first purchased for the Library of Congress, were ordered from London and arrived in 1801. The collection of 740 volumes and three maps was stored in the U.S. Capitol, the Library's first home. President Thomas Jefferson approved the first legislation defining the role and functions of the new institution on January 26, 1802.
"In the almost two centuries since its founding, the Library has taken on the mission of making its resources available and useful to the Congress and the American people, and sustaining and preserving a universal collection of knowledge and creativity for future generations. The vast holdings of the Library now number well over 110 million items."
The fact that the library was in the Capitol was a problem when the British burned the building in 1814. Later, the Library gained another presidential connection when former President Thomas Jefferson offered to sell his library to the nation to re-create the Library of Congress. A patriotic gesture, certainly, but Jefferson also needed the dough to fend off creditors.
More from the Library of Congress itself: "Jefferson's library not only included over twice the number of volumes as had been destroyed, it expanded the scope of the library beyond its previous topics—law, economics, and history—to include a wide variety of subjects in several languages.
"Anticipating the objection that his collection might be too comprehensive, he argued, "I do not know that it contains any branch of science which Congress would wish to exclude from their collection; there is, in fact, no subject to which a Member of Congress may not have occasion to refer."