By 1820, long lines of interested observers began to form at the entrance to the Senate Chamber. That year's Missouri Compromise guaranteed an equal balance in the Senate between states that permitted slavery within their borders and those that did not. Consequently, the Senate became the principal forum for debate over the issue of whether to permit the expansion of slavery into the nation's newly acquired territories and the states that would form in these areas.
In an effort to accommodate its rapidly increasing number of visitors, the Senate authorized construction of a second gallery. Soon that gallery became packed and impatient visitors pressed for overflow space on the Senate floor. In the years ahead, the Senate alternately liberalized and tightened its regulations governing special access to the floor. Between 1845 and 1850, congestion on the floor grew worse as five newly admitted states contributed 10 additional senators. Long before the availability of separate office buildings, the Senate's 62 members spent much time at their chamber desks and resented the crowding.
In September 1850, as the space situation turned critical, Congress appropriated $100,000 to add new Senate and House wings. This massive project doubled the Capitol's original space. Lasting 17 years and employing 700 workers, this became one of the largest and most expensive construction projects in 19th-century America. No other building could compare in cost, scale, complexity, and richness.
On January 4, 1859, members of the Senate solemnly proceeded to their new chamber. The next day's New York Herald described the room as light, graceful, and "finely proportioned." The iron ceiling contained 21 brilliantly adorned glass panels that emitted light through a skylight in the roof or from gas jets placed just beneath it. A special heating and ventilating system was designed to offer year-round comfort. The spacious new galleries accommodated up to 600 visitors and for several years made that chamber a popular site for off-hours theatrical events and lecture programs.
Within months of their arrival, however, members began to complain about poor acoustics, inadequate lighting, chilling drafts, and the deafening sound of rain echoing on the glass-paneled ceiling. Only the looming crisis of secession and civil war stopped plans for an immediate reconstruction of that space—but the complaining continued for at least another century.
U.S. Congress. Senate. History of the United States Capitol: A Chronicle of Design, Construction, and Politics, by William C. Allen. 106th Congress, 2d sess., 2001. S. Doc. 106-29.