Bulfinch was among the first American-born architects of distinction. A Harvard graduate and self-trained architect, he had established himself as New England's leading architect before his tenure at the Capitol. He continued Latrobe's efforts to restore the north and south wings.

Construction on the center building began under Bulfinch's direction in 1818. Although he inherited plans from Thornton and Latrobe, Bulfinch modified them according to his own ideas and taste. He designed the original low wooden dome (which was replaced by the present cast-iron dome in the mid-1850s). He also planned the Capitol Grounds and the original west terraces. In 1829 Bulfinch completed the construction of the Capitol, 36 years after the cornerstone was laid.

From 1816-67 supervision and maintenance of the Capitol were directed by the Commissioner of Public Buildings. Minor architectural services were regularly provided by Robert Mills and other Washington architects between 1829 and 1851, when there was no Capitol architect.