Special Collections in the Oliver Wendell Holmes Library holds some of Holmes's memorabilia, correspondence, and books. These include the stereoscope he invented in the 1860s, the original manuscript of “The School-Boy,” a poem that he wrote for and delivered at the Phillips Academy centennial in 1878, and some of the medical books that he owned. Oliver Wendell Holmes Jr. gave this collection to Phillips Academy in 1930.
Two reading rooms and the central hall remain as Platt intended. Georgian-style woodwork lines both the reference study area, the Garver Room, and the less formal Freeman Room. On One wall of the Freeman Room is a mural painted by Stuart Travis depciting the history of Phillips Academy overlaid on a map of Andover as it appeared in 1830. Originally the second floor housed seminar rooms and the book delivery area with access to five levels of book stacks.
In 1959 James Copley, class of 1935, donated funds for a new library wing to house materials for the intensive American history course as part of a comprehensive building campaign called The Andover Program. Designed by Benjamin Thompson of The Architects Collaborative, the Copley Wing was essentially a glass structure attached to the older brick building without disturbing it.
Thirty years later, during the late 1980s, the Copley Wing was entirely replaced with a more ambitious addition designed by Shepley, Bulfinch, Richardson & Abbot. A computer center and expanded administrative offices were integrated into the original library. In 2018-2019 another renovation (designed by Ann Beha Associates, architects, and Consigli Inc, builders) updated heating, ventilation, and air systems, added group study areas, expanded the makerspace, converted the first floor book stack into classrooms, and increased the number of seats for students. Platt's reading rooms remain popular with students and are used on a daily basis. With the primary entrance on the east, however, Platt's elegant front facade is now mostly ceremonial.