Like a painting in a frame, a grand building deserves a grand setting. The Capitol grounds had suffered as a construction site while the wings and dome were built. They were also too small for the enlarged building. Senator Justin Morrill of Vermont spearheaded efforts to improve them, calling in Frederick Law Olmsted, father of American landscape architecture (best known for New York City's Central Park).

In 1873, Congress agreed to close sections of A Street north and south and bought two adjacent squares of land, bringing the Capitol grounds to 58 acres. Olmsted designed a marble terrace for the west front, arguing that the building looked as if it might otherwise slide off Jenkins Hill. The terrace, built between 1882 and 1892, also provided committee and storage space.