Room 91B is a small San Juan period storage room built into the corner of 91W. The room measures 1.5 x 1.5 m and was apparently constructed as a storage area for Room 85B. Nineteen strata were recorded in Room 91B. Seven of these relate to various components of the walls used to enclose the room. Four strata define consecutive roof-fall units from the collapse of the structure's roof. Trash strata were defined along with other occupational fill units and a floor. One storage pit feature was recorded. The room probably functioned as a small storeroom for the adjoining Room 85B. Based on the ceramic assemblage, construction and use occurred between the mid-1100s and 1280s.