Former Workshop of Alexander Graham Bell

From www.si.edu:

Located at the corner of 35th Street and Volta Place, N.W., Bell House, erected in 1853, was purchased in 1881 by then Smithsonian Regent Alexander Graham Bell for his father. Bell maintained a laboratory in the carriage house behind the main house in which he conducted experiments focussing on gaining advances for the hearing impaired. In 1988 Bell House was acquired by the Denver-based telecommunications company US WEST as a Washington base for corporate Chairman Jack MacAllister.

Also from www.georgetowner.com:

Across the street at 1527 35th Street (southeast corner of Volta Place and 35th Street) is the former home of Alexander Graham Bell. When Dr. Bell lived in this house, he conducted experiments in the small stucco house at 3444 Volta Place (which is now a separate residence).