The Caucus Room in the Russell Senate Office Building is an excellent example of the Beaux Arts style of architectural design. Grand, well ordered, and richly detailed, the room provides a dignified environment in which important political meetings and social functions are held. It is the oldest and one of the largest assembly rooms built for the Senate outside the Capitol. Before the construction of the Russell Senate Office Building, caucuses and other meetings took place in cramped committee rooms in the Capitol.

In 1903, the Senate Office Building Commission retained the services of John Carrére and Thomas Hastings, a prominent New York architectural partnership, to design a new office building for the Senate. Their training at the Ecole des Beaux-Arts in Paris, which resulted in a thorough knowledge of classical architecture, is seen throughout the building and is particularly apparent in the Caucus Room. The room lies at the end of a progression of monumental spaces, which begin with the rotunda and continue in the marble staircases that land directly in front of the principal entrance to the Caucus Room. Through this architectural hierarchy, one is led from the building's "front door" directly and powerfully to the Caucus Room. Measuring 74 feet long by 54 feet wide, the room is treated with paired Corinthian pilasters standing on a continuous pedestal and supporting a richly detailed entablature including dentils, modillions, and egg-and-dart moldings. The rich ceiling is decorated with a variety of classical motifs—rosettes, guilloch, and Greek key—which have been recently gilded. Six windows on the courtyard wall and four crystal chandeliers light the room. The three-tiered chandeliers, which are original to the room, feature globes etched with national emblems, such as the U.S. Seal, American Indian head, and liberty cap.

In addition to party caucuses, this room has been the site of many major public hearings. Some of the most notable are listed below.