This is the only surviving example in the Capitol Hill Neighborhood of a major house in the Neoclassical style as practiced by Latrobe. Although altered through various rebuildings, it still provides the silhouette of a Federal style house constructed close to the Capitol during the city's nascent years. Robert Sewall had the house built on the corner lot of 2nd Street and Constitution Avenue NE, incorporating an existing brick structure dating from 1750. Secretary of the Treasury Albert Gallatin rented the house as both residence and offices. During the British invasion of the capital city in 1814, the house was partially burned. It was rebuilt soon after, establishing its essential form, which has endured through the years. The property remained in the Sewall family until 1922, when Porter H. Dale, senator from Vermont, purchased it and restored the house and grounds. Seven years later, Alva Belmont acquired the house as headquarters of the National Women's party. From this location, the organization lobbied Congress on women's rights issues. In 1958, when Congress voted to expand its grounds, it decided not to incorporate the house because of its historical associations.
Although many will view the Sewall-Belmont House as a spoiled Federal style house because of the extensive alterations of the late nineteenth and early twentieth centuries, it is a worthy specimen of adaptation and redesign. The house is two and a half stories over a raised basement. The balanced three-bay facade retains its Federal style articulation and its original Flemish bond walls. The mansard roof with three dormer windows was added in the late nineteenth century. The exterior staircase dates from the turn of the twentieth century. The entrance has side lights and a late nineteenth-century peacock fanlight under an early molded arch with keystone. The flat window lintels with sunken bull's-eye corner blocks, a motif employed by late eighteenth-century English Neoclassical architects, were probably introduced into this country by Latrobe. They were quickly adopted by local builders here and in Philadelphia.