Designed in the Second Italian Renaissance Revival style by the Boston firm of Allen and Collens, the William Oxley Thompson Memorial Library--also known as the Main Library--opened in 1913. The library's site was suggested by the Olmsted Brothers, designers of Central Park in New York City. As grand as the new building was, it soon began to reach the limits of its capacity to serve the needs of the growing university.
After World War II, a surge of veterans led to a dramatic increase in enrollment, and the university's administration called for a long-delayed new addition to the library. The 1951 expansion to the west took the form of a new 11-story structure, providing new study space and stack areas.
In 1966, the addition of a mezzanine floor to the once acclaimed reference hall divided it laterally in half. This effort seriously compromised the magnificence of the original building, as did a contemporary addition to the west of the stack tower in 1977. Today, much of the grandeur of the original 1913 building has been lost. With each subsequent addition and renovation, the beautiful features of the original building have become increasingly obscured. [SOURCE]