Congress was outgrowing its home. There were 15 states in the Union when the Capitol was designed. By 1850, there were 31 states. House membership increased during that period from 106 to 237.

In 1850, the Senate Committee on Public Buildings offered $500 to the architect with the best solution to the Capitol's space problems. Senators liked the idea of putting wings on the original building. House members preferred adding to the east front. Unable to agree, the House and Senate left the decision to the president. In a politically savvy move, President Millard Fillmore gave each a small victory. He asked the architect favored by the House, Thomas U. Walter of Philadelphia, to enlarge the Capitol by adding wings—as the Senate preferred.