The property was designated a National Historic Landmark as a nationally significant example of Colonial Revival architecture, built in 1901 to designs that were the result of a unique collaboration between Theodate Pope Riddle, one of the United States' first female architects, and the renowned firm of McKim, Mead & White.

Egerton Swartwout of the architectural firm McKim, Mead, and White translated her design into a working site plan, and construction took place over the period of 1898 to 1901.

Remaining as it was at the time of Theodate's death, the house is extensively furnished with paintings, prints, objets d'art, and fine furniture and rugs.

Highlights of the collection include major paintings by Eugène Carrière, Mary Cassatt, Edgar Degas, Édouard Manet, Claude Monet and James McNeill Whistler; prints including three engravings by Albrecht Dürer (Melencolia I, 1514), 17 copper plate etchings and lithographs by James McNeill Whistler, and Japanese woodblock prints by artists Katsushika Hokusai, Utagawa Hiroshige and Kitagawa Utamaro; eight bronze sculptures by Antoine-Louis Barye; about 13,000 letters and postcards including correspondence from Mary Cassatt, Henry James and James McNeill Whistler; and about 2,500 photographs, including six of Gertrude Käsebier's art photographs.

Hill–Stead's grounds were originally designed in consultation with landscape architect Warren H. Manning and feature a broad lawn with ha-ha and slate walkway; artificial pond; and formal, octagonal flower garden.