Alfred Bult Mullett was a British-American architect who served from 1866 to 1874 as Supervising Architect, head of the agency of the United States Treasury Department that designed federal government buildings. His work followed trends in Victorian style, evolving from the Greek Revival to Second Empire to Richardsonian Romanesque.

Second Empire style, also known as the Napoleon III style, is a highly eclectic style of architecture and decorative arts, which uses elements of many different historical styles, and also made innovative use of modern materials, such as iron frameworks and glass skylights. It flourished in the Second French Empire during the reign of Emperor Napoleon III (1852–1870) and had an important influence on architecture and decoration in the rest of Europe and North America. Major examples of the style include the Opéra Garnier (1862–1871) in Paris by Charles Garnier, the Bibliothèque nationale de France, the Church of Saint Augustine (1860–1871), and the Philadelphia City Hall (1871–1901). The architectural style was closely connected with Haussmann's renovation of Paris carried out during the Second Empire; the new buildings, such as the Opéra, were intended as the focal points of the new boulevards.