Founded by the Brotherhood of Demitrius at the end of the Third Age. It was filled with all knowledge up to that point. When the Brotherhood went into hiding, they continued to hoard knowledge and fill the Library's shelves.
When the majority of the Brotherhood was executed at the end of the Sixth Age, the location of the Library was lost. It was not found again until 1658 by the four remaining members of the Brotherhood. It was once again opened and knowledge began to be distributed to the world.
As the Brotherhood began to grow again, the Library served as its headquarters.