United States Capitol dome

The United States Capitol dome is the massive dome situated above the United States Capitol which reaches upwards to 288 feet (88 m) in height. The dome was designed by Thomas U. Walter, the fourth Architect of the Capitol, and constructed between 1855 and 1866 at a cost of $1,047,291. 

First dome
The cast iron dome of the United States Capitol is not the first dome to sit above the building, but the second. The origin of the first dome began with the Capitol design contest operated by Secretary of State Thomas Jefferson, at the behest of President George Washington, in 1792. The winner of the contest, Doctor William Thornton, called for a dome in his original design for the building. Most vividly, Thornton drew upon the Roman Pantheon for inspiration with the Neoclassical dome and associated portico. However, Thornton never received the chance to build the dome he envisioned. Nor, however, did Thornton's replacement as the second Architect of the Capitol, Benjamin Henry Latrobe, gain the opportunity to build the first dome for the Capitol. Rather, Latrobe was kept busy repairing, rebuilding, and completing the north and south wings of the building until his departure in 1817. Instead the job fell to Latrobe's successor, the third Architect of the Capitol, Charles Bulfinch. Bulfinch was responsible for the construction of the first dome in the nation, which he designed and built for the Massachusetts Statehouse in 1787. United States Capitol with Charles Bulfinch dome, 1846 Bulfinch began by adopting the suggestion of a drum, upon which the dome would sit, that was added to the Capitol designs by his predecessor, Latrobe. In contrast, however, the dome that eventually rose under Bulfinch's oversight was taller than any previous design and taller than his own preference. In an account written years later, Bulfinch stated that the dome was made loftier at the request of James Monroe's administration. In 1822, Bulfinch requested funds for the construction of the center of the building, and President Monroe signed off on an appropriation of $120,000. This included the building of a two-dome structure, a stone interior dome to rise 96 feet (29 m) above the rotunda floor (matching the dimensions of the Pantheon), and a wooden exterior dome that would rise to 140 feet (43 m). Set at the crown of the exterior dome was a 24 feet (7.3 m) wide oculus, which provided illumination to the rotunda floor below. Bulfinch completed the project in 1823.

For more than two decades, the green copper dome of the Capitol greeted visitors to the nation's capitol, until the 1850s. Due to the growth of the United States and the expansion and addition of new states, the size of the United States Congress had grown accordingly and pushed the limits of the capacity of the Capitol. Under the guidance of the fifth Architect of the Capitol, Thomas U. Walter, extensions were built onto the north and south wings of the building. In the process, the new, longer building made the original Bulfinch dome appear aesthetically displeasing (and had been the source of much prior criticism as well). Congress, after lobbying by Walter and Montgomery C. Meigs (then Supervising Engineer), passed legislation to build a bigger dome in 1855. 

Second (current) dome
Plans began in May 1854 to build a new cast-iron dome for the United States Capitol, sold on the aesthetics of a new dome, as well as the utility of a fire-proof one. Influenced by the great domes of Europe, Walter paid particular attention to the Pantheon of Paris, St Paul's Cathedral in London, St. Peter's Basilica in Rome and Saint Isaac's Cathedral in Saint Petersberg. William Allen, Historian of the Capitol, described Walter's first design as, "...a tall, ellipsodial dome standing on a two-story drum with a ring of forty columns forming a peristyle surrounding the lower half of the drum. The upper part of the drum was enriched with decorated pilasters upholding a bracketed attic. Crowning the composition was a statue standing on a slender, columned tholus..." Walter drafted a seven-foot (two-meter) drawing of the aforementioned design and displayed it in his office, where it drew the excited attention of members of Congress in 1854. 

A year later, on March 3, 1855, President Franklin Pierce signed off on the appropriation of $100,000 to build the dome. Construction began after some practical changes to the original design (such as the reduction of the columns from forty to thirty-six) in September of that year with the removal of the dome raised by Charles Bulfinch. A unique scaffold was built inside the rotunda, designed to keep weight away from the weak center area of the floor, and a crane was set within to run on a steam-powered engine (fueled from the salvaged wood from the old dome). Over the next eleven years, the dome designed with an interior dome and exterior dome rose over the nation's capitol. By December 2, 1863, Walter was able to set the Statue of Freedom atop the dome. This was not accomplished until after Walter had been forced to revise the design of the dome to handle the statue, which had been delivered taller and heavier than requested. Yet, the man who designed the dome did not see its total completion, due to Thomas Walter resigning in 1865. His replacement, Edward Clark, assumed the role of finishing the last aspects of the dome. Just over a month later, in January 1866, Constantino Brumidi – who had been hired to paint a fresco on a platform above the interior dome's oculus – removed the scaffolding used during his work on the Apotheosis of Washington . This signaled the end of construction for the United States Capitol dome.

Some 8,909,200 pounds (4,041.2 metric tons) of iron were ultimately used in the construction that ran virtually eleven years. Inside, the interior dome rises to 180 feet (55 m) over the rotunda floor, and outside, the exterior dome ascends to 288 feet (88 m) including the height of the Statue of Freedom. The total cost of the dome was valued at $1,047,291. Visitation of the dome is highly restricted, usually offered only to members of Congress and their select guests. Access is further restricted by the weather, since summer heat trapped under the dome may make the area unbearable. Visitors ascend a series of metal stairs between the inner and outer domes. They eventually wind their way to a balcony just underneath the Apotheosis of Washington. When looking up from the rotunda floor, you can barely make out the railing some 180 feet (55 m) above the rotunda floor.


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