The third floor was originally the master bedroom suite. Rosamond Gibson's bedroom, the largest in the house, features a bedroom set of mock bamboo that reflects the East Asian-inspired aesthetic that was popular in the late nineteenth century. From this room, Rosamond would have planned meals, managed the family’s social schedule, and overseen the hiring and firing of servants.
Houses in the Back Bay were built with indoor plumbing; in 1860, however, the bathroom on this floor only had cold running water and hot water would have been brought up by the servants.
Originally, the bathroom joined two bedrooms, one of which served as Charles Hammond Gibson, Sr.'s bedroom until his death in 1916. (Separate bedrooms were considered a luxury in this period; they allowed a married couple a measure of privacy, and they were yet another way of showing off wealth.) In 1934, Charlie, Jr. returned home and turned his father’s bedroom into his private study. He wrote and entertained close friends here.