Repairing the Bunker Hill Monument: Preserving Our Nation's Heritage

"Our historic buildings are living witnesses to the triumphs and struggles of previous generations."
-Stephanie Meeks, National Trust for Historic Preservation

Lithograph of the dedication of the Bunker Hill Monument.

"'76' Quick Step," Boston Public Library.

On June 17, 1843, the Bunker Hill Monument stood brand new. Its pristine light-gray granite shined astonishingly bright in the summer sun. Americans celebrated the opening of this giant obelisk with great fanfare. The President of the United States, John Tyler, attended the ceremony along with 100,000 spectators. Daniel Webster, the renowned orator, addressed the crowd standing before him in the public park that surrounds the Monument. On this day, Americans dedicated the Monument to the Battle of Bunker Hill and to the Provincial militia that fought and died on June 17, 1775. It was the first major battle of the American War of Independence.

The Bunker Hill Monument was popular with the public from the day it opened. Visitors came from all over to see the formidable 221-foot obelisk, the largest in the United States at the time.^[1] Many climbed the Monument's 294 interior stairs to reach an observation chamber at the top that provided four-direction views. Before long, an accompanying lodge building was constructed to house historic artifacts from the battle.

Like any structure, the Bunker Hill Monument has worn down over time. While thousands of visitors enter the Monument yearly, they have little effect on wearing down this solid-granite edifice. The weather and air pollution that regularly pummels the Monument's exterior walls are the biggest challenges to keeping the Monument in good condition.

Rain and snow have proven to be the most dangerous elements if they penetrate the exterior surface of the Monument. When water gets between the granite blocks, it can harm the granite, especially if the water repeatedly freezes and thaws. Granite blocks under these conditions may flake or shed small pieces from the surface of the granite. Also, when water seeps into the Monument, it can collect on the interior granite steps, resulting in a slipping hazard to visitors. For these reasons, the Monument must be continuously cared for and repaired.

Over time, the Monument has had three successive organizations that took on the responsibility of making repairs to the Monument. Many devoted Americans had built the Monument. Many more would be needed to regularly repair it.

The Right Stuff

Solomon Willard, architect and builder of the Bunker Hill Monument, quarried granite for the obelisk from nearby Quincy, Massachusetts. This granite had a reputation for its hardness and sturdiness. The granite blocks of the Monument are very durable and can stand up to the elements. However, the mortar between the granite blocks is vulnerable to the wearing effects of weather and air pollution.

The Bunker Hill Monument is made mostly of two things: large granite blocks and mortar. Mortar is a type of cement that is between the blocks. Mortar needs more care than the blocks.

NPS Photo

Mortar, a type of cement, creates a weatherproof seal between the granite blocks of the Monument. Workers make mortar by mixing sand, clay, lime, and other binding elements, including water. They apply mortar as a paste; when mortar dries, it hardens. Mortar fills the gaps between the Monument's granite blocks. Masonry workers had applied the mortar between the granite blocks when they built the Monument. To enhance the monolithic look of the obelisk, Willard used very large blocks of granite with a thin line of mortar between them.

The Monument is very stable. This cross view of the first level of the Bunker Hill Monument shows how all the granite blocks are linked together and also bound to the spiral staircase. The staircase is attached to the inner, circular core. All 78 levels of the Monument are arranged in a similar way.

Solomon Willard, Plans and Sections of the Obelisk on Bunker’s Hill
(Boston MA, S.N. Dickinson, 1843).

Over the years, some newspaper reporters expressed fear that worn mortar could lead to the loosening of the granite blocks of the Monument. Mortar plays only a small role in keeping the granite blocks together. Solomon Willard calculated that the blocks would stay together due to his design and their great weight.

Willard and his team created this obelisk out of three thousand interlocked granite blocks. The average block weighs five tons; some near the base of the Monument weigh ten tons. In total, the Monument weighs around 7,000 tons. A 12-foot-deep granite foundation with a 50 square foot base also helps stabilize the Monument. Surveyors in 1980 discovered that the Monument was nearly as vertical, or plumb, as when it was new.

The National Park Service, as the new caretaker of the Bunker Hill Monument, conducted a complete examination of the monument in 1980, including the foundation.

NPS Photo

Willard designed a nearly indestructible Monument. To keep it that way, workers must regularly replace deteriorated mortar, also known as "repointing" the mortar. Repointing is a painstaking job. After workers remove any loose mortar, they force new mortar between the joints to a depth of between 6 and 12 inches.

Workers often do not replace all the mortar when repointing, only the deteriorated sections, usually near the surface of the granite blocks. The Monument has over 11,000 linear feet of mortar joints that workers have maintained and continue to maintain. The importance of repointing first became evident less than thirty years after the Monument opened.

Sky Walkers

In 1870, the Monument's roof began to leak and rain filtered into the Monument. The obelisk's roof, known as the pyramidion, is the pyramid that tops the obelisk. It consists of granite blocks like the rest of the Monument.

Masonry worker repairing the Bunker Hill Monument pyramidion in 2006.

Courtesy Joseph Gnazzo Company, Inc.

As the organization that sponsored the building of the Monument, the Bunker Hill Monument Association (BHMA) faced the task of repairing the pyramidion in 1870. Since the Monument's opening, the BHMA had been charging visitors an admission fee to climb the stairs to the observation deck. They used these fees to get the roof repaired.

In 1870, the only structures as tall as the Bunker Hill Monument in Boston were church steeples and chimneys. The BHMA hired steeplejacks, workers who repaired these structures, to fix the Monument's pyramidion.

This worker repairing the Bunker Hill Monument in 1920 would be violating today’s safety rules on working from heights.

"George Stands on Pinnacle of Bunker Hill Monument - And Daily Slides the 221 Feet to Base to Get His Dinner Pail- 'Easy,' He Declares." Boston Post, July 25, 1920.

The steeplejacks likely built a wooden platform that extended out from the top windows of the Monument. From this platform, they climbed a ladder to reach the roof. While on the roof, the steeplejacks secured themselves with ropes to allow them to work over 200 feet above the ground. They could now safely replace the mortar between the granite blocks of the pyramidion. With the mortar repaired, the roof of the Monument became waterproof once more. Over the years, many have tried other products to waterproof the Monument, but mortar remains the best choice.

In the early years of the Monument, workers repairing it were responsible for their own safety. They were wise to be careful: falling from heights has always been the leading cause of death at construction jobs. In 1877, the Commonwealth of Massachusetts started implementing safety rules to protect workers from heights. Many years later, the federal government, through the Occupational Safety and Health Administration (OSHA), also acted to protect workers from falls. These are the standards that workers on the Monument follow today.

Scores of masonry workers have performed repointing projects at the Bunker Hill Monument. No worker has ever died or been seriously injured repairing the Bunker Hill Monument.

Weathering Heights

Repointing the Monument has become a routine task; workers have repointed the Bunker Hill Monument eight times, including recent preservation work in 2023. Major repointing projects occurred in 1870, 1882, 1920, 1958, 1980, 2006, 2010, and 2023. New technologies and safety standards influenced how workers performed these repointing tasks.

After its completion, the mortar slowly wore away from the Bunker Hill Monument, requiring it to be repointed in the 1870s and 1880s.

ca. 1857-1881, Boston Public Library

In 1882, newspapers in Boston and elsewhere reported that the mortar of the Bunker Hill Monument was "washed out" in places and moss was growing on the Monument. Twelve years earlier, in 1870, workers had repaired the roof of the Monument but had not attended to the rest of the obelisk. The mortar of the rest of the Monument was now forty years old.

Members of the BHMA consulted with a young engineering graduate of the Massachusetts Institute of Technology. The BHMA wanted to use the best method of suspending workers on the outside of the Monument in order to complete the repair work. No description exists of the type of staging the engineer devised but it was likely very creative. This engineer, Harry H. Cutler, acquired over 70 engineering patents during his career.

The BHMA also talked to the chief engineer constructing the Washington Monument. Lieutenant Colonel Thomas L. Casey recommended a new product called Portland cement which had components of mortar already premixed. Portland cement is still a popularly used component of mortar today.

Passing the Torch

By the early 1900s, the BHMA, the first caretaker of the Monument, had financial difficulties. Since opening the Monument in 1843, the BHMA had expanded the Monument site to include the Monument, a lodge building, iron fencing, walkways, granite steps to the site, statues, and landscaping covering about four acres of land. All these items together cost more to maintain than the Monument itself.

In 1919, the BHMA transferred ownership of the Bunker Hill Monument site to the Commonwealth of Massachusetts and its Metropolitan District Commission (MDC). State officials approved a much-needed rehabilitation project for the Monument site, including repointing the entire exterior of the Monument in 1920.

This worker repointing the Bunker Hill Monument in 1958 appears to be floating on the Monument. He's using a "cable car" that can climb up and down the side of the Monument.

Courtesy of Reverend Wolcott Cutler, Charlestown Branch, Boston Public Library

Thirty-seven years later, a local politician lamented the "utter disrepair" of the Bunker Hill Monument.^[2] More than the Monument needed maintenance; the entire site needed rehabilitation. The MDC repointed and cleaned the entire Monument and fixed all the iron fences in 1958. A couple of years later, in 1960, it repaired walkways and landscaping.

The Commonwealth of Massachusetts, like the BHMA before it, found it difficult to maintain the Bunker Hill Monument site. In 1976, the Commonwealth of Massachusetts made arrangements with the National Park Service to transfer ownership of the Monument.

Before the transfer, state officials added a notable component to the Monument site. They installed inscribed granite tablets at the four entrances to the site to commemorate the country's 200^th birthday. The inscriptions on the granite tablets establish the connection between the efforts of the Provincial militia on June 17, 1775 in the Battle of Bunker Hill and the eventual creation of the United States. The four entrances to the Monument site became known as the Massachusetts, Connecticut, New Hampshire, and United States gates.

Other projects preserved and protected the Monument between the 1980s and 2000s. In 1993, workers used a crane to repair the lightning rod of the Bunker Hill Monument.

NPS Photo / Blaise Davi.

A Fresh Start

In 1980, the staff of Boston National Historical Park, a unit of the National Park Service, recommended a major rehabilitation of the Bunker Hill Monument site. This project proved to be the costliest restoration to date. Over the course of a year, workers repointed the entire Monument, including its foundation. Additionally, workers installed a new drainage system to ensure rain no longer pooled around the foundation of the Monument. To address deterioration of the grounds, the NPS installed new walkways and new benches, while workers repaired iron fences and improved landscaping.

Mortar between the granite blocks of the Bunker Hill Monument need the most care. This is a drone view of the pyramidion of the monument in 2023. Notice the gaps in mortar that workers had to repair.

NPS Photo

A generation later, the Monument and grounds once again required restoration work. Between the years 2006 and 2010, workers performed some major tasks. In 2006, masons repointed the north and east sides of the Monument; they completed the south and west sides in 2010. Workers also relocated the main entrance to the Bunker Hill Lodge to the south side of the building.

Masonry contractors bring their own ideas on how to scale the Bunker Hill Monument to make repairs. This is the 2010 repointing of the Monument.

Courtesy PJ Spillane Company, Inc.

This new entrance provided an accessible large ramp for visitors. Other work at the site included masonry workers rebuilding the granite steps at the four gates to the Monument grounds. Lastly, to align with this restoration, the NPS opened a new Bunker Hill Museum in 2007 in the former Charlestown branch of the Boston Public Library, which stands across the street from the Monument.

Workers wrapped the Bunker Hill Monument in steel scaffolding in the fall of 2023.

NPS Photo

Continued Devotion

By 2023, rain once again had entered the Monument from its pyramidion because of worn mortar. Workers assembled a scaffolding system that surrounded the exterior of the Monument from bottom to top. Masons repointed the pyramidion and the top ten levels of the Monument.

This work has been in preparation for upcoming commemorations. On June 17, 2025, many people will gather on the Monument grounds, to honor the 200^th anniversary of the laying of the Monument’s cornerstone. Also in 2025, the National Parks of Boston, partners, community members, and visitors will reflect on the 250^th anniversary of the Battle of Bunker Hill. In 2026, they will gather again for the 250^th anniversary of our nation’s independence.

In 2023, Masonry workers repointed the granite blocks at the top of the obelisk, known as a pyramidion. The photo depicts the new mortar drying on the pyramidion.

NPS Photo

The Monument is over 180 years old. Its three successive caretakers (the BHMA, the MDC, and the NPS) have been devoted to its care. Repointing the mortar between the granite blocks of the Monument is the major challenge in preserving it. The granite of the Monument is very durable, but mortar starts to break down after about 30 years; mortar on the pyramidion lasts for an even shorter time. Additionally, safely suspending workers on the outside of the Monument to perform the repointing has proven to be a challenge.

In 1961, the National Park Service designated the Bunker Hill Monument as a National Historic Landmark, marking the Battle of Bunker Hill as a significant event in the history of the United States. As the first large obelisk built in the US, the Monument is also a notable American architectural achievement. The National Park Service is committed to maintaining this icon of liberty in perpetuity.

It's a daunting challenge; the Monument colossus needs regular care. Like previous caretakers of the site, the NPS is dedicated to keeping the site open year-round in a condition that is safe and enjoyable for its hundreds of thousands of annual visitors. On behalf of all Americans and with their unflagging support, the NPS preserves the Bunker Hill Monument because it is a significant part of Americans' shared heritage and values.

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Footnotes

[1] The Bunker Hill Monument was surpassed in size by the Washington Monument in 1888, 45 years after the Bunker Hill Monument opened.

[2] Gerard F. Doherty, "Historic Shrine Not Forgotten," Boston Globe. April 1, 1957, p.16.

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