United States Capitol dome in the context of "Rotunda (architecture)"

The United States Capitol, often called the Capitol or the Capitol Building, is the seat of the United States Congress, the legislative branch of the federal government. It is located on Capitol Hill at the eastern end of the National Mall in Washington, D.C. Although no longer at the geographic center of the national capital, the U.S. Capitol forms the origin point for the street-numbering system of the district as well as its four quadrants. Like the principal buildings of the executive and judicial branches, the Capitol is built in a neoclassical style and has a white exterior.

Central sections of the present building were completed in 1800, when the 6th U.S. Congress convened there on November 17, 1800, moving the national capital from Philadelphia to Washington, D.C.. The building was partly destroyed in the 1814 Burning of Washington by the British, then was fully restored within five years. The building was enlarged during the 19th century, by extending the wings for the chambers for the bicameral legislature as more states were admitted to the union, with the House of Representatives housed in the south wing and the Senate housed in the north wing. The massive dome was completed around 1866 just after the American Civil War. The east front portico was extended in 1958. The building's Visitors Center was opened in the early 21st century.

Separation of powers is a political doctrine originating in the writings of Charles de Secondat, Baron de Montesquieu in The Spirit of the Laws, in which he argued for a constitutional government with three separate branches, each of which would have defined authority to check the powers of the others. This philosophy heavily influenced the United States Constitution, according to which the Legislative, Executive, and Judicial branches of the United States government are kept distinct to prevent abuse of power. The American form of separation of powers is associated with a system of checks and balances.

During the Age of Enlightenment, philosophers such as Montesquieu advocated the principle in their writings, whereas others, such as Thomas Hobbes, strongly opposed it. Montesquieu was one of the foremost supporters of separating the legislature, the executive, and the judiciary. His writings considerably influenced the Founding Fathers of the United States, such as Alexander Hamilton and James Madison, who participated in the Constitutional Convention of 1787, which drafted the Constitution.

The United States Capitol building features a central rotunda below the Capitol dome. Built between 1818 and 1824, the rotunda has been described as the Capitol's "symbolic and physical heart".

The rotunda is connected by corridors leading south to the House of Representatives and north to the Senate chambers. To the immediate south is the semi-circular National Statuary Hall, which was the House of Representatives chamber until 1857. To the northeast is the Old Senate Chamber, used by the Senate until 1859 and by the Supreme Court until 1935.

The Statue of Freedom, also known as Armed Freedom or simply Freedom, is a bronze statue designed by Thomas Crawford that, since 1863, has crowned the United States Capitol dome. Originally named Freedom Triumphant in War and Peace, a U.S. government publication now states that the statue "is officially known as the Statue of Freedom." The statue depicts a female figure bearing a military helmet and holding a sheathed sword in her right hand and a laurel wreath and shield in her left.

Thomas Ustick Walter (September 4, 1804 – October 30, 1887) was an American architect. He worked on more than 400 projects, including Moyamensing Prison and Girard College in Philadelphia. He served as the fourth Architect of the Capitol, and led the addition of the north and south wings and the central dome. He retired in 1865, but financial difficulties forced him back to work in the 1870s, including a job as Chief Assistant to the Architect of Philadelphia City Hall.

A founder of the American Institute of Architects, he served as its president from 1876 to 1887.