By 1850 so many new states had joined the Union that the U.S. Senate and House of Representatives had outgrown their chambers. Congress addressed the problem by authorizing the addition of grand wings to the north and south ends of the Capitol, and replacing the old copper dome with a much larger, magnificent cast-iron one. Philadelphia architect Thomas U. Walter designed the additions and, along with engineer Montgomery C. Meigs, supervised construction. On December 2, 1863, the last section of the Statue of Freedom was placed on top of the dome, although work still continued on the interior of the Capitol. This 1863 engraving by Henry Sartain anticipated the completion of the building and also envisioned the end of the Civil War by depicting an idyllic setting. The son of John Sartain–a preeminent portrait engraver who is considered the father of mezzotint engraving in America–Henry Sartain engraved only a few images before establishing a printing business devoted to producing engravings by his father and others. It is believed his father assisted him in completing this Capitol view.