Washington Monument made from material gneiss
Excavation and initial construction
Construction of the monument finally began three years later in 1848 with the excavation of the site, the laying of the cornerstone on the prepared bed, and laying the original foundation around and on top of the cornerstone, before the construction of its massive walls began the next year. Regarding modern claims of slave labor being used in construction, Washington Monument Historian John Steele Gordon stated "I can't say for certain, but the stonemasonry was pretty highly skilled, so it's unlikely that slaves would've been doing it. The stones were cut by stonecutters, which is highly skilled work; and the stones were hoisted by means of steam engines, so you'd need a skilled engineer and foreman for stuff like that. Tending the steam engine, building the cast-iron staircase inside—that wasn't grunt work. ... The early quarries were in Maryland, so slave labor was undoubtedly used to quarry and haul the stone" Abraham Riesman, who quoted Gordon, states "there were plenty of people who worked as skilled laborers while enslaved in antebellum America. Indeed, there were enslaved people who worked as stonemasons. So the possibility remains that there were slaves who performed some of the necessary skilled labor for the monument." According to historian Jesse Holland, it is very likely that African-American slaves were among the construction workers, given that slavery prevailed in Washington and its surrounding states at that time, and slaves were commonly used in public and private construction.Gordon's arguments are valid for the second phase (1879–1888) after slavery was abolished, when every stone laid required dressing and polishing by a skilled stonemason. This includes the iron staircase which was constructed 1885–86. That the stonecutters in the quarry were slaves is confirmed because all quarry workers were slaves during the construction of the United States Capitol during the 1790s.: 5–6  However, Holland's views are valid for the first phase because most of its construction only required unskilled manual labor. No information survives concerning the method used to lift stones that weighed several tons each during the first phase, whether by a manual winch or a steam engine.: 17–23  The surviving information concerning slaves that built the core of the United States Capitol during the 1790s is not much help. At the time, the District of Columbia outside of Georgetown was sparsely populated so the federal government rented slaves from their owners who were paid a fee for their slaves' normal daily labor. Any overtime for Sundays, holidays, and nights was paid directly to the slaves which they could use for daily needs or to save to buy their freedom.: 9  Conversely, the first phase of the monument was constructed by a private entity, the Washington National Monument Society, which may not have been as magnanimous as the federal government, but most information was lost during the 1850s while two Societies vied for control of the monument. Useful information concerning the use of slaves during the major expansion of the Capitol during the 1850s, nearly contemporaneous with the monument's first phase, does not exist.
Only a small number of stones used in the first phase required a skilled stonemason, the marble blocks on the outer surface of the monument (their inner surfaces were left very rough) and those gneiss stones that form the rough inner walls of the monument (all other surfaces of those inner stones within the walls were left jagged). The vast majority of all gneiss stones laid during the first phase, those between the outer and inner surfaces of the walls, from very large to very small jagged stones, form a pile of rubble held together by a large amount of mortar. The top surface of this rubble can be seen below at Walls in an 1880 drawing made just before the polished/rough marble and granite stones used in the second phase were laid atop it. The original foundation below the walls was made of layered gneiss rubble, but without the massive stones used within the walls. Most of the gneiss stones used during the first phase were obtained from quarries in the upper Potomac River Valley. Almost all the marble stones of the first and second phases came from two Maryland quarries about 20 miles (30 km) north of downtown Baltimore in rural Baltimore County where stone for their first Washington Monument was obtained.On Independence Day, July 4, 1848, the Freemasons, the same organization to which Washington belonged, laid the cornerstone (symbolically, not physically).: 45, 136–143  According to Joseph R. Chandler:: 136, 140–141 
No more Washingtons shall come in our time ... But his virtues are stamped on the heart of mankind. He who is great in the battlefield looks upward to the generalship of Washington. He who grows wise in counsel feels that he is imitating Washington. He who can resign power against the wishes of a people, has in his eye the bright example of Washington.
Two years later, on a torrid July 4, 1850, George Washington Parke Custis (1781–1857), the adopted son of George Washington and grandson of Martha Washington (1731–1802), dedicated a stone from the people of the District of Columbia to the Monument at a ceremony that 12th President Zachary Taylor (1784–1850, served 1849–1850) attended, just five days before he died from food poisoning.Walls
During the first phase of construction (1848–1854), the walls were built with bluestone gneiss rubble, ranging from very large irregular stones having a cross section of about 5 by 10 feet (1.5 m × 3.0 m) down to spalls (broken pieces of stone) all embedded in a large amount of mortar. The outer surface is marble stones 14 to 18 inches (36–46 cm) thick in 2-foot (61 cm) high courses or rows horizontally encircling the monument. Although each course contains both stretchers (stones parallel to the wall) and headers (stones projecting into the wall), about two to three times as many stretchers as headers were used. Their joints were so thin that some stones pressed on bare stone below them, breaking off many pieces since it was constructed. The batter or slope of the outer surface is 0.247 inches per foot (2.06 cm/m, 1°11'). The inner surface has disorderly rows of smaller roughly dressed bluestone gneiss.: B-49 : sheets 7–30 : 18–19, 23, 105–6  The base of the first phase walls has an outer dimension of 55 feet 1+1⁄2 inches (16.80 m) square and a thickness of 15 feet (4.6 m). The interior well is 25 feet 1 inch (7.65 m) square and has square corners. The weight of the first phase walls up to 150 feet (45.7 m) is 22,373 long tons (25,058 short tons; 22,732 tonnes).During the second phase (1879–1884), the walls were constructed of smoothly dressed (ashlar) large marble and granite blocks (rectangular cuboids) laid down in an orderly manner (Flemish bond) with thick joints. Two-foot high marble surface stones, using an equal number of stretchers and headers, were backed by granite blocks from the 152-foot level (the first course above the rubble) to the 218-foot level, where marble headers become increasingly visible on the internal surface of the walls up to the 450-foot level, above which only marble stones are used.
Between the 150- and 160-foot levels the inner walls rapidly slope outward, increasing the shaft well from 25 feet 1 inch square to 31 feet 5+1⁄2 inches (9.59 m) square with a corresponding decrease in the thickness of the walls and their weight.: sheets 4–5 : 23  The second phase walls at the 160-foot level were 8 feet 7+1⁄2 inches (2.63 m) thick, which, combined with the larger shaft well, yields an outer dimension of 48 feet 8+1⁄2 inches (14.85 m) square at that level. The top of the second phase walls are 34 feet 5+1⁄2 inches (10.50 m) square and 1 foot 6 inches (46 cm) thick.: 3–7  The second phase interior walls have rounded corners (2-foot (0.61 m) radii). The weight of the second phase walls (from 150 feet to 500 feet) are 21,260 long tons (23,810 short tons; 21,600 tonnes). The walls of the entire shaft (combined first and second phases) are 500 feet 5+1⁄8 inches (152.530 m) high.The first phase of the walls was constructed under the direction of William Dougherty. Its white Cockeysville marble exterior came from the Texas quarry now adjacent to and east of north I-83 near the Warren Road exit in Cockeysville, Maryland. The quarry was named for the Texas Station (no longer extant) and 19th-century town on the Northern Central Railway. During the first phase it was operated by Thomas Symington, but is now operated by Martin Marietta Materials and no longer produces building stone. The second phase of construction was under the direction of Lt Col/Col Thomas Lincoln Casey of the United States Army Corps of Engineers, who removed two defective courses added by the Know-Nothings and the last 152-foot course added by Dougherty before Casey began his construction. The next three courses of white marble (152–156 feet (46–48 m)) came from Sheffield, Massachusetts, while all courses above them came from the Beaver Dam quarry just west of the 19th-century town of Cockeysville.: 63  The latter quarry is located on Beaver Dam Road near its intersection with McCormick Road. During the second phase the quarry was operated by Hugh Sisson, but is now flooded, is called Beaverdam Pond, and is the home of the Beaver Dam Swimming Club. Both 19th-century towns are now within the city limits of Cockeysville.Miscellaneous details
The total cost of the monument from 1848 to 1888 was $1,409,500 (equivalent to $30,000,000 in 2021). The weight of the above ground portion of the monument is 44,208 long tons (49,513 short tons; 44,917 tonnes),  whereas its total weight, including the foundation below ground and any earth above it that is within its outer perimeter is 81,120 long tons (90,854 short tons; 82,422 tonnes). The total number of blocks in the monument, including all marble, granite and gneiss blocks, whether externally or internally visible or hidden from view within the walls or old foundation is over 36,000. The number of marble blocks externally visible is about 10,000.
The monument stands 554 feet 7+11⁄32 inches (169.046 m) tall according to the National Geodetic Survey (measured 2013–14) or 555 feet 5+1⁄8 inches (169.294 m) tall according to the National Park Service (measured 1884). In 1975, a ramp covered two steps at the entrance to the monument, so the ground next to the ramp was raised to match its height, reducing the remaining height to the monument's apex. It is both the world's tallest predominantly stone structure and the world's tallest obelisk. It is the tallest monumental column in the world if all are measured above their pedestrian entrances, but two are taller when measured above ground, though they are neither all stone nor true obelisks. The tallest masonry structure in the world is the brick Anaconda Smelter Stack in Montana at 585 feet 1+1⁄2 inches (178.35 m) tall. But this includes a 30-foot (9.1 m) non-masonry concrete foundation, leaving the stack's brick chimney at 555 feet 1+1⁄2 inches (169.20 m) tall, only about 6 inches (15 cm) taller than the monument's 2015 height. If the monument's aluminum apex is also discounted, then the stack's masonry portion is 15 inches (38 cm) taller than the monument's masonry portion.
constructed from material fabricated from material composed of material formed from material manufactured from material