Washington Monument

The Washington Monument is a obelisk and monument on the National Mall in Washington, D.C., built to commemorate George Washington, a Founding Father of the United States, victorious commander-in-chief of the Continental Army from 1775 to 1783 in the American Revolutionary War, and the first President of the United States from 1789 to 1797. Standing east of the Reflecting Pool and the Lincoln Memorial, the monument is made of bluestone gneiss for the foundation and of granite for the construction. The outside facing consists, due to the interrupted building process, of three different kinds of white marble: in the lower third, marble from Baltimore County, Maryland, followed by a narrow zone of marble from Sheffield, Berkshire County, Massachusetts, and, in the upper part, the so-called Cockeysville Marble. Both "Maryland Marbles" came from the "lost” Irish Quarry Town of "New Texas". It is both the world's tallest predominantly stone structure and the world's tallest obelisk, standing tall, according to U.S. National Geodetic Survey measurements in 2013–2014. above the pre-construction ground level. The foundation is surrounded by a grassy knoll, which serves as a buttress for the monument's foundation and effectively places the monument's foundation below ground level. * according to the National Geodetic Survey (NGS) using the criteria of the Council on Tall Buildings and Urban Habitat (CTBUH), that is, from the "level of the lowest, significant, open-air, pedestrian entrance" to the highest point of the building. From among four candidate points suggested by the NGS, the CTBUH chose a point on the entry ramp installed in 1975 where it crosses the outer face of the marble facade of the monument.15, 318, 413, B49, figs 3.32, 3.33, 3.39, 3.42}} Measured 2013–14 and reported . This is also its new above-ground height because the ground at the shaft was raised in 1975 to match the ramp. The ground surrounding the shaft was replaced by granite pavers during 2004–05 to match the raised ground level and the ramp. This height is above four "CASEY marks", brass bolt heads whose shafts are inserted vertically into the topmost level of the foundation just outside the four corners of the monument. These CASEY marks were set flush with the lower surface of the marble blocks. The NGS thinks they were likely used by Col. Thomas Lincoln Casey, the engineer in charge of construction, to determine the traditional height in 1884. The floor at the elevator is now above this pedestrian entrance, and above the CASEY marks. The highest point of the monument is a one-millimeter-diameter dimple atop the aluminum apex. * according to the National Park Service. Measured and reported in 1884 by Col. Thomas Lincoln Casey, the engineer in charge of construction. It was measured from the top of the foundation (the lowest marble joint or the door-sills of the two empty doorways), which was in place in 1884. This is the traditional height of the monument that became moot when the pavement or ground next to the monument was raised in 1975. * according to architectural drawings in the ''Historic American Buildings Survey'' (1994), pavement at shaft to tip. This height is comparable to the NGS height because it was also determined after the ramp was installed in 1975. None of these heights include a set of lightning rods surrounding the monument's aluminum apex. An old set was installed in 1934, which protruded above its tip by . In 2013 a new set of lightning rods was installed which protrude above the apex by about . }} It is the tallest monumental column in the world if all are measured above their pedestrian entrances. A traditional method is above a part of the monument comparable to ground level. A more recent method is that used by the Council on Tall Buildings and Urban Habitat (CTBUH), the arbiter of the height of tall buildings since 1969. CTBUH states the height of a building must be measured above the "level of the lowest, significant, open-air, pedestrian entrance". Under this measurement, the Washington Monument is the tallest, followed by the San Jacinto Monument at and the Juche Tower at . The above-ground heights of the three monumental columns from tallest to shortest are the San Jacinto Monument (), the Juche Tower (), and the Washington Monument. Height differences are relative to the height of the Washington Monument. * The Washington Monument's CTBUH (above pedestrian entrance) height, , is the same as its above ground height. * The San Jacinto Monument has a surveyed height of from its footing to the top of its beacon. However, the architect of the monument, Albert C. Finn, stated, "San Jacinto ... is actually from the first floor to the top of the beacon" ... in the "customary way" of measuring such things. The "first floor" is the CTBUH criterion. A stepped terrace elevates this pedestrian entrance above ground, thus reducing the monument's remaining height by its thickness, about , to the monument's CTBUH height. The monument is made of reinforced concrete, not stone, although it has a facade of limestone. * The Juche Tower has a specified height of above a very large concrete bus parking lot just east of the tower. A stepped terrace elevates its pedestrian entrance, also on its east side, above this ground level. Its thickness, , reduces the remaining height of the tower to , its CTBUH height. The tower is made of reinforced concrete, not stone, although it has a facade of granite. A metal cage holding many panels of red glass in the shape of a flame, internally illuminated, surmounting a gold-colored "fuel chamber", occupies its top .}} It was the world's tallest structure between 1884 and 1889, after which it was overtaken by the Eiffel Tower, in Paris. Previously, the tallest structures were Lincoln Cathedral (1311–1548; 525 ft) and Cologne Cathedral (1880–present; 515 ft).

Construction of the presidential memorial first began in 1848. The construction was suspended however from 1854 to 1877 due to funding challenges, a struggle for control over the Washington National Monument Society, and the American Civil War. The stone structure was completed in 1884, and the internal ironwork, the knoll, and installation of memorial stones was completed in 1888. A difference in shading of the marble, visible about or 27% up, shows where construction was halted and later resumed with marble from a different source. The original design was by Robert Mills from South Carolina, but construction omitted his proposed colonnade for lack of funds, and construction proceeded instead with a bare obelisk. The cornerstone was laid on July 4, 1848; the first stone was laid atop the unfinished stump on August 7, 1880; the capstone was set on December 6, 1884; the completed monument was dedicated on February 21, 1885; it was open on the October 9, 1888.

The Washington Monument is a hollow Egyptian-style stone obelisk with a column surmounted by a pyramidion. Its walls are thick at its base and thick at their top. The marble pyramidion's walls are thick, supported by six arches: two between opposite walls, which cross at the center of the pyramidion, and four smaller arches in the corners. The top of the pyramidion is a large, marble capstone with a small aluminum pyramid at its apex, with inscriptions on all four sides. The bottom of the walls, built during the first phase from 1848 to 1854, are composed of a pile of bluestone gneiss rubble stones (not finished stones) held together by a large amount of mortar with a facade of semi-finished marble stones about thick. The upper of the walls, built in the second phase, 1880–1884, are of finished marble surface stones, half of which project into the walls, partly backed by finished granite stones.

The interior is occupied by iron stairs that spiral up the walls, with an elevator in the center, each supported by four iron columns, which do not support the stone structure. The stairs are in fifty sections, most on the north and south walls, with many long landings stretching between them along the east and west walls. These landings allowed many inscribed memorial stones of various materials and sizes to be easily viewed while the stairs were accessible (until 1976), plus one memorial stone between stairs that is difficult to view. The pyramidion has eight observation windows, two per side, and eight red aircraft warning lights, two per side. Two aluminum lightning rods, connected by the elevator support columns to groundwater, protect the monument. The monument's present foundation is thick, consisting of half of its original bluestone gneiss rubble encased in concrete. At the northeast corner of the foundation, below ground, is the marble cornerstone, including a zinc case filled with memorabilia. Fifty American flags fly on a large circle of poles centered on the monument. In 2001, a temporary screening facility was added to the entrance to prevent a terrorist attack. An earthquake from Virginia in 2011 slightly damaged the monument, and it was closed until 2014. The monument was closed for elevator repairs, security upgrades, and mitigation of soil contamination in August 2016 before reopening again fully in September 2019. Provided by Wikipedia