It was founded to house the private library of J. P. Morgan in 1906, which included manuscripts and printed books, some of them in rare bindings, as well as his collection of prints and drawings. The library was designed by Charles McKim of the firm of McKim, Mead and White and cost $1.2 million. It was made a public institution in 1924 by J. P. Morgan's son John Pierpont Morgan, Jr., in accordance with his father's will.
The Morgan has one of the world's greatest collections of ancient Near Eastern cylinder seals, small stone cylinders finely engraved with images for transfer to clay by rolling. It also contains many music manuscripts and a considerable collection of Victoriana, including one of the most important collections of Gilbert and Sullivan manuscripts and related artifacts.
According to wikipedia.