Appleton set about immediately to document the house with measured drawings and photographs. By August 1, 1916, Appleton persuaded fifteen individuals to underwrite Historic New England’s purchase of Otis House and provide funds to begin the repairs. As the funds were raised, Appleton began to restore the house. His extensive correspondence, many bills, estimates, and a few architectural drawings document the process. Though it was not an auspicious time to raise funds for the restoration because of the United States’ imminent entry into World War I, Appleton was constant in his appeals. It took until 1920 to secure the money and complete the repairs. During this time, floors were replaced, wallpapers were stripped and preserved, woodwork was repaired, and original windows, shutters, and plaster were repaired or replicated.
There was still a row of shops on the land between the Otis property and Cambridge Street, housing a cobbler, a barber, a plumber, and a laundry. The shops were purchased in 1919 with the intention of removing them.
Interrupting the restoration process, Otis House received notice in 1925 that the City of Boston was going to widen Cambridge Street. The new lanes were planned to go directly through the front of Otis House. The four c. 1840 row houses directly behind Otis House, numbers 10, 12, 14, and 16 Lynde Street, were purchased. The two southernmost buildings (numbers 10 and 12) were demolished to make room for the relocated Otis House.
Otis House was separated from its foundation, supported by steel beams, and rolled back on large wooden rolling pins. The house was rolled back from the street forty-two feet, eleven inches. The process took an entire week and resulted in the preservation of the original structure, as well as joining the 1796 house with the two surviving row houses behind.
A new foundation and cellar were designed by Little and Browne, Architects. The row houses were remodeled for office and library use, while most of the rest of the space was used as museum space.
Various restorations, repairs, and remodeling projects took place as the needs of the office, archive, and storage spaces changed throughout the twentieth century. Otis House again escaped demolition in the late 1950s and early 1960s when the West End neighborhood bordering the property was razed as part of a Boston Redevelopment Authority urban renewal project.
Restoring Otis House has been a slow and continual process. In the late 1960s and early 1970s, pioneering work in chemical paint analysis was done at Otis House, which led to some surprising discoveries about Federal-era tastes. Using the results of this analysis, Otis House has been restored to accurately reflect those tastes. In addition, fragments of original wallpaper were reproduced and hung, with finishing touches taken from sources such as inventories of similar houses and furnishings that appear in paintings of Federal-era homes. Most of the house now appears as it might have looked when the Otises lived here. In 2000 rooms were remodeled to tell the stories of Dr. and Mrs. Mott and the Williams sisters.
Over the years Otis House has changed to conform to the atmosphere of the neighborhood. From a large mansion in a wealthy neighborhood, to a clinic in an increasingly commercial area, to a boarding house in a working class district, the house has seen many trends come and go.
Unlike most of its neighbors, however, Otis House has withstood the changes even as buildings around it were torn down. Today it stands as a memorial to the Bowdoin Square and West End neighborhoods and the early history of Beacon Hill.