Washington Monument STATISTICS

Designed by Robert Mills
Total weight of monument: 90,854 tons
Depth of foundation: 36 feet 10 inches
Area of foundation: 16,002 square feet
Total number of blocks in monument: 36,491
Cost of monument: $1,187,710
Total height of monument: 555 feet, 5 ½ inches
Height of monument in meters: 169.25
Height from lobby to observation level: 500 feet or 50 stories
Thickness of monument walls at base: 15 feet , at observation level: 18 inches
Corner stone laid: July 4, 1848
Phase One (1848 - 1858): To the 152 foot level, under the direction of Superintendent William Daugherty.
Phase Two (1878 - 1888): Work completed by the U.S. Army Corps of Engineers, commanded by Lt.Col. Thomas L. Casey.
First stone at 152 foot height laid: August 7, 1880
Capstone set: December 6, 1884
Dedicated: February 21, 1885
Number of memorial stones in stairwell: 193
Officially opened to the public: October 9, 1888
Present elevator installed: 1998
Elevator ascent/descent time: 60 seconds/60 seconds
 Type of stones on exterior: white marble primarily from Baltimore, Maryland; a few blocks from Sheffield, Massachusetts
Type of stones in the interior: Granite from Maine
Number of steps in stairwell: 897

LATER IMPROVEMENTS AND ADDITIONS
1901: The steam-powered elevator was replaced by an electrical one, which could run from the base to the top in five minutes carrying 35 passengers.
1904: The lobby was developed with mosaic and marble wainscot flooring, electrical lights, steam heating, and four oak settees for the comfort of the visitors in their long wait for the elevator.
1926: Bars were placed on the windows of the observation level to prevent suicides from occurring. A new elevator was installed.
1929: The first searchlights, to outline the top of the monument to air traffic, were installed. In 1931, aircraft-warning lights were hung from the observation windows to replace the searchlights. In 1958, holes were cut a few feet above the windows and the warning signals were positioned there for better visibility.
1937: The circle of flags were placed around the monument. As the number of states increased, more flags were added. Today there are 50 flags surrounding the monument representing the 50 states. 1958: Floodlights were installed on the grounds around the monument to light it up against the night sky. 1959: A new elevator was installed that could ascend in 70 seconds from the ground to the observation level, and descend in 60 seconds carrying 40 passengers.

1972: Revolving glass doors were installed at the western end of the entrance corridor.
1974: Floor, stair and structural repairs took place and a new air temperature control system was installed. The revolving doors were replaced by standard glass ones. At the same time, the pyramidion windows were equipped with