Charles Bulfinch of Boston took over the restoration from Latrobe in 1818. The north and south wings reopened in the fall of 1819. Work on the middle building (connecting the wings) began on August 24, 1818, the fourth anniversary of the British fire. It concluded eight years later.

Bulfinch designed and built the rotunda, or "grand vestibule," which stood 96 feet across and 96 feet high—the proportions of Rome's ancient Pantheon. On the outside, he built a very tall wooden dome, responding to President James Monroe's request for a prominent and visible structure. Bulfinch also landscaped the Capitol's 22-acre garden and built earthen terraces on the west front. When Bulfinch retired in 1829, the Capitol was finished—36 years after George Washington had laid its cornerstone.