Congress needed more space, but no one wanted the beloved Capitol overshadowed by its new additions. Secretary of State Daniel Webster suggested using narrow corridors to connect the new wings, leaving the old building visually intact. People also felt it important that the wings appear to grow naturally from the older building.

On the inside of the wings, no attempt was made to imitate the old interiors. Instead, modern designs and materials were used. Marble staircases led to spacious galleries overlooking the new chambers, which featured highly decorated iron ceilings and stained-glass skylights. Doors and windows stood in elaborate—and fireproof—cast-iron frames. English encaustic tile (embedded with colorful patterns) paved the floors, a vivid contrast to the brick and stone floors of the old building.