President 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 in 1800 when President John Adams signed an act of congress.

At first, a small library was housed in the U.S. Capital, in the Senate wing in Wasington, D.C.. The original collection consisted of 740 books ordered from London and three maps. Gradually the library acquired more and more books. However most of the original collection of approximately 3,000 books were destroyed by the British in 1814 during the War of 1812. As a result, the library sought to restore its collection in 1815.

One of the major contributors to the restoration project was former US President Thomas Jefferson (1743-1826). His entire collection was bought in 1815- a personal collection of 6,487 books. Unfortunately, after a period of slow growth, another fire struck the library in its U.S. Capital chambers in 1851, again destroying a large number of books including a number of Jefferson's collection.

Jefferson's collection was purchased for $23,950. He had spent 50 years accumulating a wide variety of books in several languages and on subjects such as philosophy, history, law, religion, architecture, travel, natural sciences, mathematics, studies of classical Greece and Rome, modern inventions, hot air balloons, music, submarines, fossils, agriculture and meteorology.

More Info: en.wikipedia.org