The Sewall-Belmont House was built by Robert Sewall in 1799-1800 and was named for him and for Alva Belmont, whose financial contribution enabled the National Woman's Party to purchase the house. It has been the headquarters of the National Women's Party since 1929. The house was designated a National Historic Site by an Act of Congress in 1974. That act also provides for the restoration, preservation, and maintenance of the house in cooperation with the National Park Service.