In the east wing, part of the third floor was removed to create a two-story well for a natural history museum and a skylight cut in the roof to provide light. With construction of Palmer Laboratory and Guyot Hall these facilities were no longer needed, and in 1911, Nassau Hall began to be used for administrative offices; President Hibben (1912-1932) was the first president to have his office there. By 1924, when Eno Hall was completed and the Department of Psychology had departed, Nassau Hall was devoted entirely to offices of the central administration.

In 1967 additional space was obtained by flooring over the two-story well in the east wing, and the exterior appearance improved by the removal of the skylight above it.

Source: Leitch p. 328ff