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The first congressional office buildings were constructed immediately after the turn of the 20th century to relieve overcrowding in the interior of the then century-old United States Capitol. Previously, members who wanted office space had to rent quarters or borrow space in committee rooms. In March 1901, Congress authorized Architect of the Capitol Edward Clark (1822-1902, served 1865-1902), to draw plans for fireproof office buildings for both the House and Senate adjacent north and south to the Capitol grounds. By two years later, in March 1903, the acquisition of land for sites, razing of the private residences and businesses and construction of the buildings were authorized. In April 1904, the prominent New York City architectural firm of Carrère and Hastings was retained. Thomas Hastings (1860-1929), took charge of the southside House Office Building project, while John Carrère (1858-1911), oversaw the construction of an almost identical office building (now named the Russell Senate Office Building) for the United States Senate to the north. Their Beaux Arts / Classical Revival styles of architecture designs were restrained complementary to the original Capitol of 1792-1863.

The Cannon Building was occupied during the session of the 60th U.S. Congress in December 1907. By less than a decade later in 1913, however, the House had already outgrown the available office space, and fifty-one rooms were added to the original structure by raising the roof and constructing a fifth floor (not visible in its exterior view). that is visible only from the enclosed court and otherwise obscured on the building's exterior public face. Originally there were 397 offices and fourteen committee rooms in the Cannon Building; the subsequent second 1932 remodeling project resulted in 85 two- or three-room suites, 10 single rooms, and 23 committee rooms. During the late 1960s, the House Beauty Shop, a salon which catered to Congresspersons, their spouses, and employees, was relocated to the Cannon House Office Building from the adjacent smaller and newer Longworth House Office Building of 1930-1933, under the auspices of the House of Representatives Beauty Shop Committee.

In January 2015, a top-to-bottom renovation of the Cannon House Office Building began. Completion is expected to take ten years and cost $752.7 million dollars. Initially, this renovation project will be focused on upgrading the building infrastructure and utilities, but will progress on to a wing-by-wing exterior and interior reconstruction. According to Bill Weidemeyer (Superintendent of the House), the building "is plagued by safety, health, environmental and operational issues that are rapidly worsening. Many of the building’s systems are original from the 1908 construction."

Architecturally, the elevations are divided into a rusticated base and a colonnade with an entablature and balustrade. The colonnades with thirty-four Doric columns that face the Capitol are echoed by pilasters on the sides of the building, and very inspired by the Louvre Colonnade in Paris. The Cannon Building is faced with marble and limestone; while the Senate's Russell Building's base and terrace are gray granite.

Modern for its time, the building initially included such facilities as forced-air ventilation systems, steam heat, individual lavatories with hot and cold running water and ice water, telephones, and electricity. Both the Cannon Building and the Russell Building are connected to the Capitol by underground passages.

Of special architectural interest is the rotunda. Eighteen Corinthian columns support an entablature and a coffered dome, whose glazed oculus floods the rotunda with natural light. Twin marble staircases lead from the rotunda to an imposing Caucus Room, which features Corinthian pilasters, a full entablature, and a richly detailed ceiling.

The north-south Cannon Tunnel connects the Cannon House Office Building to the Capitol. The tunnel is lined with artwork from the annual Congressional Art Competition for high school students. Branching off the entrance to the Cannon Tunnel is a separate tunnel southwest to the adjacent Longworth House Office Building, and entrances to a cafeteria, shoe shiner/cobbler, and a Legislative Resource Center. Unlike the tunnels from the Capitol to the Senate Office Buildings on the northside and the Rayburn Tunnel, the Cannon Tunnel because of its age, has no subway line, and is primarily a pedestrian pathway. In addition, a separate tunnel runs between the Cannon building and to the east of the neighboring James Madison Memorial Building, a part of the adjacent Library of Congress buildings complex.

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  Construction of Cannon Tunnel, north-south from Capitol to Cannon Building, c. 1904
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  Cannon Building rotunda
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  Aerial view looking southeast of Cannon House of Representatives Office Building from Capitol dome
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  Aerial view looking west (Capitol at right / north, out of view) of the Cannon House Office Building in 2015 while undergoing latest renovation (scaffold crane in center courtyard). Longworth House Office Building adjacent and further west at top of photo. Rayburn House Office Building barely seen at photo top to the far west.

 This article incorporates public domain material from Cannon House Office Building. Architect of the Capitol.

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