Dupont Circle became Washington's most fashionable address in the last quarter of the 19th century. The development of what had been an outlying area of working class shanties, slaughterhouses, and a brickyard was spurred by the public works improvements inaugurated by "Boss" Alexander R. Shepherd in the early 1870s, including street paving, tree planting and the laying of water and sewer lines.
Among the first investors was a syndicate of California mine owners, one of whom, Curtis J. Hillyer, built a house on the site now occupied by the Townsend Mansion. The social cachet of the area was set with the building of the British Embassy just south of Dupont Circle at Connecticut and N Street in 1875. Within the next several decades Dupont Circle was ringed with the mansions of families who had made their fortunes elsewhere but wished to establish a social presence in the nation's capital.
The Townsend Mansion is one of five surviving, exceptionally grand, residences that were built around 1900 within two blocks of Dupont Circle. Although the side streets of the Dupont Circle area are lined with townhouses of varying sizes and degrees of individuality, houses built on Dupont Circle and along the near blocks of Massachusetts Avenue were generally freestanding and much larger. They were designed for entertaining on a lavish scale and their hostesses were important figures on Washington's social scene.
The Townsend Mansion was built by Mary Scott Townsend, daughter of William L. Scott, a Pennsylvania railroad and coal magnate who became a member of Congress. As an heiress to his fortune, she was a woman of great wealth. She became one of Washington's social leaders, known for her elegant entertaining. Mrs. Townsend's husband, Richard H. Townsend, died shortly after the house was completed, but she continued to live there until her death in 1931.
Mrs. Townsend's only child, Mathilde Townsend Welles, and her husband, B. Sumner Welles, President Franklin D. Roosevelt's Under Secretary of State (from 1937 to 1942), maintained the mansion until World War II when it was leased to the Canadian Women's Army Corps. The Cosmos Club purchased the building from Mrs. Welles's estate in 1950.