The westernmost part of the grounds is the Capitol Reflecting Pool, which reflects the Capitol and the Ulysses S. Grant Memorial.
With the exception of the Ford and O'Neill House Office Buildings, all House and Senate office buildings within the Capitol Complex are linked to the Capitol via an underground network of people movers or footpath tunnels.
Construction of the Capitol began in 1792. When built, it was the only existing building for the use by the nation's legislature. In addition to Congress, the building was also designed to house the Library of Congress, the Supreme Court, the district courts, and other offices.
Following the completion of the building and as the nation grew, so did the size of the Congress. The Capitol and its grounds were enlarged accordingly, and by 1892 the building had reached essentially its present size and appearance (with the exception of the east front extension 1958–1962 and courtyard infill areas 1991–1993).
Even with the enlargements, Congress eventually grew too big for the building and new facilities had to be constructed to meet the needs of the government. With the moving of the Library of Congress into its own building in 1897, and with the construction of new office buildings for the House and Senate in the early 20th century, the Capitol Complex was born.
Known simply as the "House Office Building" and "Senate Office Building" when they opened in 1908 and 1909, the Cannon House Office Building and Russell Senate Office Building became the first buildings solely for use as offices by the House of Representatives and the Senate. These new buildings were heated and provided with electricity by the new Capitol Power Plant which opened in 1910 and is still used today.
Aerial view of the United States Capitol Complex, c. 1923
The 1930s was a decade of major construction within the growing Capitol Complex. In 1933 alone the U.S. Botanic Garden Conservatory, Director's residence, and Bartholdi Park were completed; the Senate Office Building's First Street wing, which had been omitted during construction for funding reasons, was added; and the Additional House Office Building (later named the Longworth House Office Building) was occupied. The Supreme Court at last found a permanent home when its own building was completed in 1935. The last building constructed within the complex in this decade was the Library of Congress Annex, now named the John Adams Building, which opened in 1939.
Within twenty years, attention returned to the need for more Congressional office space; this led to the construction of a second building for the Senate (now named the Dirksen Senate Office Building), which was completed in 1958. The House's third building, the Rayburn House Office Building, opened in 1965.
Capitol Complex (in foreground, 2007) looking west toward the National Mall
Renovations to the Botanic Garden Conservatory began in September 1997 and continued for four years until December 2001 when the building reopened. The Conservatory's aluminum framework, glazing, interior floors, doors, and lighting were replaced; all electrical, plumbing, and environmental control systems were upgraded, and air conditioning was added to the display halls.
The newest addition to the Capitol Complex is the Capitol Visitor Center. Despite many delays, the Center opened in December 2008, and includes an exhibition gallery, two theaters, a dining facility, and gift shops. The budget for construction of the center was $584 million.
On January 6, 2021, the Capitol was stormed by supporters of President Donald Trump after a rally in front of the White House. A Capitol Police officer was wounded and was pronounced dead a day later at a nearby hospital. Additionally, one of the protesters was shot and later pronounced dead at a nearby hospital. A further three deaths from medical emergencies were reported while over a hundred injuries were reported by Capitol Police.
