Special treasures include the largest portion of President George Washington's library from Mount Vernon; Jean-Antoine Houdon busts of Washington, Benjamin Franklin, and Lafayette once owned by Thomas Jefferson; a first edition copy of John James Audubon's The Birds of America; a 1799 set of Francisco Goya's Los caprichos; portraits by Gilbert Stuart, Chester Harding, and John Singer Sargent; and one of the most extensive collections of contemporary artists' books in the United States.

[4] The Boston Athenaeum is also known for the many prominent writers, scholars, and politicians who have been members, including Ralph Waldo Emerson, Nathaniel Hawthorne, Louisa May Alcott, Oliver Wendell Holmes Sr., Oliver Wendell Holmes Jr., John Quincy Adams, Margaret Fuller, Francis Parkman, Amy Lowell, John F. Kennedy, and Edward M. Kennedy.

The first librarian, William Smith Shaw, and the new trustees had ambitious plans for the Athenaeum, basing their vision on the Athenæum and Lyceum in Liverpool, England.

Their vision was expanded to include a library encompassing books in all subjects in English and foreign languages, a gallery of sculptures and paintings, collections of coins and natural curiosities, and even a laboratory.

This ambitious design has developed over the past two hundred years with some changes in focus (e.g., there is no chemistry lab) but remaining true to the ideal expressed in the institution's seal, chosen in 1814: Literarum fructus dulces, meaning "Sweet are the Fruits of Letters."

[5] At first, the Boston Athenaeum rented rooms, then in 1809 bought a small house adjacent to the King's Chapel Burying Ground, and in 1822 moved into a mansion on Pearl Street, where a lecture hall and gallery space were added within four years.

The architect was Edward Clarke Cabot, an artist and dilettante whose design was selected because his ingenious ground-level arch over graves in the Granary Burial Ground allowed more space on all floors above the basement level.

The Athenaeum's exhibition area opened up when the Museum of Fine Arts moved the collections into their own space overlooking Copley Square.

In the years 1872–1876, Boston's Museum of Fine Arts exhibited in the Athenaeum's gallery space while awaiting the completion of its new building's construction.

[14][15][16] The mission of the Boston Athenaeum is to engage all who seek knowledge by making accessible the library's collections and spaces, thereby inspiring reflection, discourse, creative expression, and joy.

The Athenaeum's holdings currently include over 600,000 volumes, and the collections' strengths focus on Boston and New England history, biography, British and American literature, as well as fine and decorative arts.

[19] A few examples from the many collections in the digital library: Since 2013, the Athenaeum has made its extensive on-going lecture series available to a wider audience through Vimeo, an open video platform.