Cannon House Office Building

Until 1908, many representatives who wanted office space had to borrow space in committee rooms in the Capitol or rent quarters; otherwise, they worked from their desk in the House Chamber. The Sundry Civil Appropriation Act (3 Stat. 1156) of March 1901 authorized the Architect of the Capitol to draw plans for a fireproof building adjacent to the grounds of the Capitol to be used for offices and storage.

On March 3, 1903, Congress appropriated construction funds and created the House Office Building Commission, composed of three representatives appointed by the Speaker of the House, to oversee the project. Representatives Joseph G. Cannon, who was elected Speaker later in 1903, William P. Hepburn, and James D. Richardson comprised the commission. Subject to their approval, Architect of the Capitol Elliott Woods was responsible for the letting of contracts and constructing the building.

The commission chose Square 690, bounded by Independence Avenue, First Street SE, New Jersey Avenue, and C Street SE for the building. After title was secured for the government, the site was cleared by the Rezin W. Darby Company of Washington, D.C. Brennan Construction Company and Cranford Paving Company began excavation on July 18, 1903. The problem of disposing of such an enormous amount of soil was solved when the Commission of the District of Columbia agreed that the site of Union Station, then under construction, could be used as a fill area. To facilitate this transfer of fill, a narrow-gauge rail-road was constructed across the Capitol's East Plaza.

In April 1904, on Woods's recommendation, the commission hired the prominent New York architectural firm of Carrère and Hastings as consulting architects. One partner, Thomas Hastings, took charge of the House office building project, while John Carrère oversaw the construction of a similar office building for the Senate. The firm had a well-established working relationship with the Architect of the Capitol; they had worked together on the redesign of the Capitol space formerly occupied by the Library of Congress.

Carrère and Hastings intended the House and Senate office buildings to complement the more important Capitol. The restrained classical designs of the office buildings were not meant to compete architecturally with either the Capitol or the Library of Congress. Accordingly, the buildings' heights are limited, and the elevations facing the Capitol grounds are identical and reserved.

At hearings in March 1905, the commission accepted John Carrère's proposal that the exterior of both buildings be faced with white marble. He testified:

I think that these two sides and the Capitol are part and parcel with each other and of each other, and should be in harmony as to design material and purpose and in every other element that enters into the conception.

For the House office building, the Independence and New Jersey Avenue fronts were faced with marble from South Dover, New York; the C Street and First Street elevations with Georgia marble; and the court fronts with limestone from Bedford, Indiana.

The exterior of the Cannon Building is reminiscent of the Colonnade du Louvre in Paris. Architecturally, the elevation is divided into two parts: a rusticated base and, supported by it, a colonnade with an entablature and balustrade. The thirty-four Doric columns on the Independence Avenue colonnade are echoed by pilasters on the New Jersey Avenue facade.

Construction of the building was complicated by the Washington Terminal Company, which had been granted an easement to build a twin railway tunnel for the Pennsylvania Railroad Company under the south-east corner of the building site.

In order to support the building with much of its foundation over this tunnel, engineers had to drive concrete pilings 26 feet deep. The Guastavino Company used patented techniques to construct a masonry vault in the building. The company brought to the U.S. a tradition of Catalan vault-building with roots in masonry techniques from around the Mediterranean. Multiple layers of thin tile laid with Portland cement in a herringbone pattern create a beautiful arch; more importantly, such vaults are strong and fireproof, quick to construct, and require fewer building materials. The Guastavino Company built a similar vault in the Russell Senate Office Building and completed structural tile vaults and a spiral staircase for the Supreme Court building. The vault in the Cannon Building supports the weight of the building's Rotunda.

The Cannon Rotunda, an area of special architectural interest in the building's interior, is located at the main entrance of the building and has a diameter of 57 feet 4 inches. Eighteen Corinthian columns on a marble arcade draw the eye upward and support a richly detailed entablature and coffered dome. The oculus of the dome is glazed to flood the Rotunda with natural light.

At the rear of the Rotunda, twin marble staircases lead to the imposing Caucus Room. The room is nearly 4,000 square feet, and its noteworthy architectural features include giant-order Corinthian pilasters, a full entablature, and a richly detailed ceiling ornamented with various classical motifs. The four crystal chandeliers bear unique glass shades patterned with designs that reference decorative motifs in the Capitol and period symbols of the United States. The Cannon Building provided larger committee rooms than the Capitol contained, which permitted larger audiences to observe hearings; perhaps most famously, the Caucus Room hosted some of the House Un-American Activities Committee hearings in the 1950s. In 2022, House Resolution 1495 designated the room as the Speaker Nancy Pelosi Caucus Room in honor of Speaker Nancy Pelosi.

The building was designed in the form of a hollow trapezoid to admit light to inner offices. On each floor the mahogany doors of the offices flank a 12-foot-wide corridor. There were 397 offices, one for each representative in the 61st Congress, and 14 committee rooms.

Offices featured crown molding and averaged 16 feet wide and 23 feet long. Mahogany furnishings included carefully crafted roll-top desks, chairs of various types, a table, a rug and cabinets. A modern building for its time, it boasted such facilities as a forced-air ventilation system, steam heat, individual lavatories with hot and cold running water and ice water, telephones and electricity. Additional amenities included a barber-shop, gymnasium, bathing rooms, a post office, a telegraph office, a dining room and a cafeteria. A tunnel provided a quick underground route to the Capitol.

The 60th Congress occupied the building in January 1908. The House, by resolution, directed the Speaker to appoint a select committee of five Members to arrange for distribution of rooms. The committee decided to assign rooms in the manner prescribed by House Rule XXXII, which regulated the drawing of seats in the House Chamber. Consequently, the act of May 28, 1908, established a seniority-based lottery system to determine the order in which Members claimed rooms and offices in the House office building.

By 1913 the House had outgrown the office space in the building. Rooms were added to the original structure by raising the roof and constructing a fifth floor. The building is now 826,465 square feet.

With the increasing need for space, it was decided in 1924 to construct another building (now named the Longworth Building) and to renovate the old one. This remodeling, completed between August and November of 1932, resulted in 171 two-room suites, 14 three-room suites, 10 single rooms, and 23 committee rooms. Other improvements and changes to the Cannon Building included:

• 1933–1938: Air conditioning installed and elevators replaced
• 1955: 308-car garage constructed in the courtyard
• 1966: Reconfiguration of suites following construction of the Rayburn House Office Building

The Cannon Renewal Project, taking place from 2014 through 2025, involves a thorough renovation of the entire building and addresses accessibility and structural issues. The project will conserve and repair the exterior and interior stone and wood, rehabilitate office spaces, and complete a comprehensive infrastructure upgrade, including heating, cooling, lighting, plumbing, fire, and life safety systems. The work also includes the removal of the previous fifth-floor addition—the marble flooring was preserved, however—before building a new, more expansive fifth floor. Window sashes, frames, interior doors, and door hardware were restored and modernized. The tiling in the Guastavino vault was cleaned and its original buff color revealed. Work is proceeding in phases, with three-quarters of the building occupied at all times.

On May 21, 1962, Public Law 87–453 renamed the three House office buildings, which had been referred to simply as the "Old," "New," and "Additional." The "Old" House Office Building's namesake, Joseph Gurney Cannon of Illinois, was Speaker of the House of Representatives (1903-1911) when the building was constructed.