Established in L’Enfant’s plan as a place of significance, the monument was intended to align with the visual axes of the President’s House (White House) and Capitol Building. In the 1840s the Washington National Monument Society selected Robert Mills’ 600-foot masonry obelisk to honor George Washington. The monolith’s weight necessitated its relocation east of center, upon a prominent knoll. The cornerstone was laid in 1848, but its completion was delayed until 1888.
The monument’s 72-acre grounds changed frequently throughout the 19th and 20th centuries. In 1851, Andrew Jackson Downing suggested an Evergreen Garden for Monument Park as part of his vision for the Mall. The McMillan Commission’s 1902 plan rectified the skewed axis by proposing formal parterre gardens and water features, with recreational amenities south of the monument. The Sylvan Theater was carved into a grove of trees nearby in 1917. The intersecting ellipses surrounding the monument were designed by the National Capital Park and Planning Commission in 1932, with planting completed by the Works Progress Administration.
A 1965 master plan by SOM sought to return the grounds to their monumental formality. Following the terrorist attacks in September 2001, Olin Partnership employed curving granite walls designed to a comfortable seat height that would also restrict vehicles. Careful regrading accommodated sweeping concrete pedestrian paths that brought visitors to the granite plaza at the monument’s base, and canopy and flowering tree plantings were renewed. The Washington Monument was listed in the National Register of Historic Places in 1966.