Congress' decision in 1850 to enlarge the Capitol sparked an intense debate about where to place the additions and where to locate the new chambers within the additions. Senators favored a plan to add wings to the north and south ends of the existing structure. House members backed a different proposal. They advocated a single new addition attached to the building's east front. Placement of such a wing on the level and spacious east plaza would avoid the expense and trouble of dealing with the sloping, unstable ground that the wings would occupy. Unable to agree, the two houses asked the president to decide.
On May 1, 1851, President Millard Fillmore decided to enlarge the Capitol by adding north and south wings, the scheme the Senate favored. A question remained about the location of the chambers within their wings. On the Senate side, some favored the northeastern corner, in the present-day location of the Lyndon Johnson and Senate Reception rooms. Others advocated the northwestern corner to isolate the rooms from the noise, dust, and smells of the east plaza's horse and carriage traffic. President Fillmore agreed with this latter group and chose the northwestern location for its fresh air and pleasant views.
Construction of the Capitol extension began in 1851. In 1853, President Franklin Pierce agreed to a revised plan for positioning the chambers. In order to isolate legislators from outside noise and to improve circulation into and out of the chambers, they were relocated to the center of their respective wings. Instead of windows letting in light and fresh air, skylights illuminated the chambers and steam-powered fans ventilated them. Soon after the Senate occupied the new chamber in 1859, however, members began to complain about its poor lighting and inferior ventilation. Although the Senate in 1860 defeated as impractical a plan to move the room to the northwest corner, senators would revive the window issue from time to time well into the twentieth century.