Which architect designed the U.S. Capitol's cast-iron dome?

Thomas U. Walter designed the U.S. Capitol’s present cast-iron dome. The dome replaced an earlier, much smaller structure after the Capitol was expanded in the 1850s and the original proportions no longer suited the enlarged building.

Walter, the Capitol’s fourth Architect, designed a double-dome system: an inner dome visible from the Rotunda and an outer dome carrying the Statue of Freedom. Construction began in 1855 and continued through the Civil War, with the statue installed in 1863. The dome was completed in 1866, after Walter had resigned and Edward Clark finished the project.

A common mix-up is Charles Bulfinch, who designed the earlier timber-framed, copper-covered dome completed in 1823. Benjamin Latrobe and William Thornton were also important in the Capitol’s earlier design history, but neither designed the current cast-iron dome. The ironwork was fabricated by Janes, Fowler, Kirtland & Co. of New York.