Washington Monument

1848 CE - 1884 CE

1848-1884

Deviations from the Original Architectural Plan

Robert Mills's original 1836 design was far more ornate than the completed structure, featuring a 250-foot diameter circular colonnade at the base and a statue of George Washington in a chariot. Due to funding shortages, the Washington National Monument Society abandoned the colonnade in 1848, opting for a plain obelisk. During the second phase, architect Thomas Lincoln Casey further simplified the design by smoothing away Egyptian-style winged sun carvings and asps that had been planned for the doorways. The final structure was also adjusted to conform more strictly to classical Egyptian proportions.

National memorial

Internal Gallery of Commemorative Stones

The monument's interior walls contain 194 memorial stones donated by states, cities, foreign nations, and benevolent societies. These stones are primarily marble, granite, and limestone, but also include exotic materials like native copper from Michigan, petrified wood from Arizona, and jadeite from Alaska. Notable contributions include a stone from Ottoman Sultan Abdul Mejid I and two stones from Utah bearing the name 'Deseret.' While most stones are visible from the stairs or elevator, one stone on the south wall is difficult to view, and two 'height stones' mark specific elevations reached during construction.

Subterranean Foundation Strengthening

During the second phase of construction, Lieutenant Colonel Thomas Lincoln Casey determined the original foundation was insufficient for the monument's projected 40,000-ton weight. To stabilize the structure, engineers added a 13-foot-6-inch thick unreinforced concrete slab beneath the original bluestone gneiss rubble foundation, increasing the load-bearing area by 2.5 times. This process involved digging 4-foot wide drifts in pairs to maintain balance. The reinforced foundation now reaches a total depth of 36 feet 10 inches below the lowest marble course, ensuring the load does not exceed 9 long tons per square foot.

Tri-Phased Marble Construction and Coloration

The monument's exterior features three distinct shades of white marble, reflecting a construction process interrupted for over two decades. The bottom 152 feet, built between 1848 and 1854, utilizes Cockeysville Marble from the Texas Quarry in Maryland. After work resumed in 1879, a small section of marble from Sheffield, Massachusetts, was added before quality issues forced a switch. The remaining 390 feet were completed using marble from the Beaver Dam quarry. These variations in source material created the visible color difference between the lower third and the upper sections of the obelisk.

Complex Engineering of the Pyramidion

The 55-foot-tall pyramidion at the monument's summit employs a weight-saving design consisting of marble panels only 7 inches thick. These slabs do not support the weight of those above them; instead, they transfer their load to the shaft walls via twelve internal marble ribs. The structure is topped by a 3,300-pound marble capstone featuring a cubical keystone and a deep groove to secure the topmost slabs. This capstone is further surmounted by an aluminum apex, which originally served as the primary lightning rod and is inscribed with 'Laus Deo' on its eastern face.

The Rare Metal Aluminum Apex

Cast by William Frishmuth in 1884, the 100-ounce aluminum apex was the largest single piece of aluminum in the world at a time when the metal's value was comparable to silver. Before installation, it was displayed at Tiffany's in New York, where visitors could 'step over' the monument's top. The apex has lost approximately 3/8 inch of its tip due to lightning strikes between 1885 and 1934. Although it remains connected to the internal iron columns via copper rods, it was effectively decommissioned as a lightning rod in 2013 when two new aluminum rods were installed to shield it.

Labor and the Use of Enslaved Workers

Historical evidence indicates that enslaved African Americans likely participated in the monument's first phase of construction. While the highly skilled stonemasonry required for the outer marble facing was likely performed by free artisans, the quarrying and hauling of stone in Maryland and Virginia heavily utilized slave labor. During the 1790s, all workers at the quarries for the U.S. Capitol were enslaved, and similar practices prevailed during the monument's early years. However, the second phase of construction (1877–1888) required advanced dressing and polishing for every stone, making the use of enslaved labor during that period unlikely.

Impact of the 2011 Virginia Earthquake

The 5.8 magnitude earthquake on August 23, 2011, caused over 150 cracks in the monument, including a significant fissure at the pinnacle. Debris was dislodged both internally and externally, and several stone lips holding the pyramidion's slabs were damaged. Repairs costing $15 million—funded equally by public taxes and a donation from David Rubenstein—involved installing stainless steel brackets to secure the pyramidion and using 'Dutchman patches' for stone repair. The monument remained closed for nearly three years, reopening in May 2014, though subsequent elevator reliability issues caused further closures through 2019.

Deviations from the Original Architectural Plan

Robert Mills's original 1836 design was far more ornate than the completed structure, featuring a 250-foot diameter circular colonnade at the base and a statue of George Washington in a chariot. Due to funding shortages, the Washington National Monument Society abandoned the colonnade in 1848, opting for a plain obelisk. During the second phase, architect Thomas Lincoln Casey further simplified the design by smoothing away Egyptian-style winged sun carvings and asps that had been planned for the doorways. The final structure was also adjusted to conform more strictly to classical Egyptian proportions.