In 1791, Pierre L’Enfant, a French-born artist, developed a plan for a new government city along the Potomac River, choosing Jenkins Hill for the “Congress House.” Secretary of State Thomas Jefferson renamed both the hill and the proposed building after Rome’s Capitoline Hill, the site of the ancient temple to Jupiter Optimus Maximus Capitolinus. Jefferson then suggested that those submitting designs for the new Capitol should evoke the Pantheon, a second century domed temple to all Roman gods. William Thornton, a Scottish-trained physician living in the West Indies, submitted the winning design, incorporating elements of the Pantheon into the section between the legislative chambers, with a low dome centered on columns supporting a classic pediment. These design elements were modified, but all were included in the original Capitol, which was finally completed in 1818 after being damaged in the War of 1812.
By 1850, Congress had outgrown the legislative chambers and approved adding a new chamber at each end of the existing Capitol. The existing dome then appeared too small in relation to the larger building. Thomas Walter based the design of a new dome on the Paris Pantheón, built to honor Genevieve, the patron saint of Paris. Like the Pantheón, the Capitol now incorporates a “double dome,” the inner section scaled to fit the original rotunda and the outer section scaled to the larger exterior. An oculus atop the inner dome opens to an elaborate fresco inspired by the Pantheón’s Apotheosis of Genevieve. The Apotheosis of Washington, picturing George Washington amidst a number of Roman gods, including Mercury and Venus, was painted by Greek-Italian artist Constantino Brumidi, once employed by Pope Gregory XVI,
Because the cast iron was showing signs of deterioration, the Capitol dome has been under repair since 2014. The history of the dome and illustrations of the Capitol designs since 1792 can be reviewed in the massive underground visitors’ center, opened in 2008.