Thomas Ustick Walter was the dean of American architecture between the 1820 death of Benjamin Latrobe and the emergence of H. H. Richardson in the 1870s. He was the fourth Architect of the Capitol and responsible for adding the north (Senate) and south (House) wings and the central dome that is predominantly the current appearance of the U.S. Capitol building. Walter was one of the founders and second president of the American Institute of Architects. In 1839, he was elected as a member to the American Philosophical Society.

Benjamin Henry Boneval Latrobe was an Anglo-American neoclassical architect who immigrated to the United States. He was one of the first formally trained, professional architects in the new United States, drawing on influences from his travels in Italy, as well as British and French Neoclassical architects such as Claude Nicolas Ledoux. In his thirties, he immigrated to the new United States and designed the United States Capitol, on "Capitol Hill" in Washington, D.C., as well as the Old Baltimore Cathedral or The Baltimore Basilica,. It is the first Cathedral constructed in the United States for any Christian denomination. Latrobe also designed the largest structure in America at the time, the "Merchants' Exchange" in Baltimore. With extensive balconied atriums through the wings and a large central rotunda under a low dome which dominated the city, it was completed in 1820 after five years of work and endured into the early twentieth century.