Last updated: July 26, 2024
Article
Bunker Hill Monument: By The Numbers
The Bunker Hill Monument stands as a memorial to those who gave their lives at the Battle of Bunker Hill. It’s also a symbol of American unity and a fixture of the New England landscape. The Bunker Hill Monument Association first envisioned this Monument in 1825, and appointed architect Solomon Willard to lead the project. The Bunker Hill Monument is a construction marvel. Workers used mostly hand tools to build the Monument in an era before there were power tools. To build the first half of the Monument, horses helped lift the granite blocks into place. Workers used a newly invented steam engine for lifting heavy blocks to finish the Monument.
The Bunker Hill Monument was the largest obelisk in North America until the completion of the Washington Monument in 1888. The Washington Monument is more than twice as tall as the Bunker Hill Monument.
Today, visitors stand in awe of the Bunker Hill Monument, and many of them ask about its story and architectural features. Click on the labels in the diagram below to learn about the different sections of the Monument.
1. Apex
The Apex is the top point of the Monument. The height of the monument has no significance. The founders of the Bunker Hill Monument Association felt they could only afford an obelisk 220 feet tall. The lines of mortar between the blocks added another foot or so to the height of the Monument.
2. Pyramidion
The Pyramidion is an equally sided pyramid that traditionally tops an obelisk. The Bunker Hill Monument’s pyramidion is not as ornate as the pyramidions of ancient times. The Egyptians often covered the pyramidions of pyramids and obelisks with a reflective material like gold or silver to bring attention to the almighty power of the sun.
The pyramidion experiences a lot of weathering and therefore needs to be restored every couple decades. Workers most recently restored the pyramidion in 2023.
- Height of obelisk to base of pyramidion: 208ft 5in or 63.5m
- Sides of the base of pyramidion: 15ft or 4.5m
- Vertical height of pyramidion: 13ft or 4.0m
- Number of courses in pyramidion: 6
- Number of courses to base of pyramidion: 78
3. Chamber
The Chamber, also known as the observation deck, is the room at the top of the Monument where visitors can look outside the Monument's windows. The interior of the Monument is small and around 25 people can make the chamber feel crowded. The National Park Service limits the amount of people who can be in the narrow stairway and in the chamber of the Monument at any one time due to safety and comfort concerns.
- Height of chamber: 18ft or 5.5m
- Diameter of chamber: 11ft 6in or 3.5m
4. Exterior Wall
The exterior wall is constructed out of granite blocks. Each singular level of granite blocks is known as a "course." During construction, workers had to reduce the diameter of each course of the Monument by over 2 inches so that the Monument narrowed as it reached skyward.
The exterior wall, including the pyramidion, gets the most weathering out of all the Monument’s components. It must be maintained every 25 years or so using a process called “repointing." The vents on the north side of the Monument are essential for admitting light and air into the Monument’s interior.
- Thickness of wall at the top: 2ft or .6m
- Sides of the square at base of pyramid: 15ft or 4.6m
- Thickness of wall at the base: 6ft or 1.8m
- Sides of the square, first course: 30ft or 9.1m
- Height of each course in obelisk: 2ft 8in or .81m
- Amount each course diminishes: 2.25in or 5.7cm
- Number of vents in North wall: 7
5. Central Cone
The central cone could be called a monument within a monument; it is over 196 feet tall and built of over 800 small granite blocks. The central cone has two main functions: it helps support the granite circular stairway, and the hollow center of the cone helps to ventilate the Monument.
The central cone is connected to the exterior wall by the spiral stairway. This connection helps keep the sections of the Monument together. There are 2 courses of cone blocks per one course of exterior wall blocks; the height of each cone block is 1ft 4in and the height of each exterior wall block is 2ft 8in.
- Height of the cone, to chamber floor: 196ft 9in or 60m
- Height of each course in cone: 1ft 4in or .41m
- Number of courses in cone: 147
6. Circular Stairway
The circular stairway allows staff and visitors to walk up and down the Monument.
The stairway has 294 steps. The number 294 has no significance. It simply was the number of 8-inch granite steps needed to bring visitors from ground level to the chamber of the Monument.
The Monument has no elevator. Elevator technology was not available in 1843 when the Monument was completed.
- Height of riser in each step: 8in or 20cm
- Number of rotations in the circular stairway: 8
Solomon Willard, Plans and Sections of the Obelisk on Bunker's Hill. Charles Cook Lithographer, Boston 1843.
7. Foundation
The Monument has a huge foundation to help ensure that it stays upright and stable for years to come. The foundation reaches 12 feet below ground. The foundation is pyramid-shaped and consists of 6 courses of granite blocks. The base course of the foundation is 50 feet square, and the foundation gradually narrows as it reaches the first course of the Monument above ground, which is 30-feet square. The foundation is made of 1,400 tons of granite, almost a quarter of the weight of the entire Monument, which is about 6,000 tons. Some foundation granite blocks are 12 feet long.
- Depth of foundation: 12ft or 3.65m
Sources
- Cassibry, Kimberly. “Obelisks and Ancient Rome”. smarthistory, the center for public art history. smarthistory. Accessed July 25, 2024.
- Isler, Martin. Sticks, Stones, and Shadows: Building the Egyptian Pyramids. University of Oklahoma Press, 2001.
- Willard, Solomon. Plans and Sections of the Obelisk on Bunker's Hill. Charles Cook Lithographer, Boston 1843.
- Wheildon, William. Memoir of Solomon Willard: Architect and Superintendent of Bunker Hill Monument. Boston: Bunker Hill Monument Association, 1865.