The Washington Monument is one of the outstanding engineering feats and still considered the finest historical monument in Washington, D.C. The pyramidion is 555 feet in height and weighs 300 tons. It was built entirely of fine-grained marble that was quarried at the Beaver Dam Quarry in Baltimore County, MD, and delivered to Washington by the Baltimore and Ohio Railroad.
Work began in June 1884 on the pyramidion by assembling materials and the machinery needed in its construction. It is constructed of 262 separate pieces of marble, containing 3,764 cubic feet of dressed stock. In December 1884 the mammoth structure was lifted into place without incident and in one piece.
To complete the obelisk, the aluminum capstone weighing 100 ounces, the largest single piece of aluminum cast to that time, was placed atop the pyramidion on Saturday, December 6, 1884.
Prior to delivery of the capstone in Washington, it was placed on exhibit at Tiffany's in New York City where it was placed on the floor and persons could have the dubious prestige of "jumping over the top of the Washington Monument." Engraved on the four sides of the capstone was the official record of the construction of the monument. The west face read: "Corner Stone laid on bed of foundation, July 4, 1848. First stone at height of 152 feet laid August 7, 1880. Capstone set December 6, 1884"; and the east face read "LAUS DEO". Laus Deo is Latin for "Praise be to God".