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.

Robert Poole (1818-1903) was an Irish-born engineer, inventor, entrepreneur, and benefactor. In 1843 he founded an ironworks in Baltimore, Maryland. For his workforce he hired members of what would become the first generation of modern metalworkers —an emerging trade whose numbers would swell to 250,000 nationally by the end of the 19th century. His enterprise became the largest of its kind in Maryland, with 800–850 employees, and, from the 1850s on, played a central role in the manufacture of iron-based infrastructure essential for private enterprise and public works in America.