The collections are available for use by the general public, in keeping with the Baltimorean merchant and philanthropist George Peabody's goal to create a library "for the free use of all persons who desire to consult it".

[3] The institute was originally planned to open in 1860, but border-state conflict in the region caused by the American Civil War delayed its establishing and construction until 1866.

[5] The current library structure in the East Wing was designed by famed local architect Edmund G. Lind and opened to the public in 1878.

The main collection reflects broad interests but is focused on the 19th century, in keeping with Peabody's desire for it to be "well furnished in every department of knowledge and of the most approved literature".

[10] The visually stunning, monumental neo-Greco interior features an atrium that, over an alternating black and white slab marble floor, soars 61 feet high to a latticed skylight of frosted heavy glass, surrounded by five tiers of ornamental black cast-iron balconies (produced locally by the Bartlett-Hayward Company[11]) and gold-scalloped columns containing closely packed book stacks.