On the library's fourth floor is the Thomason Room, a walnut-paneled room that contains the university's special collections, incuding rare books on special subjects, the Criminal Justice Special Collection, and the drawings and manuscripts of John. W. Thomason, Jr., for whom the room was named.

After the opening of AB4, and the relocation of the library science department, the library's first, third, and fourth floors were remodeled in 2003 to provide additional space for offices, conference rooms, and collection areas.  As part of this consolidation, university archives moved to the fourth floor from the Peabody building.