Excavating the North Grove

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An archaeological dig north of the Mansion yielded fascinating, and intriguing, artifacts.

In late 2022, the Archaeology team began excavating the North Grove in preparation for the expansion of the existing subterranean bunker that houses the Mansion’s HVAC (heating, ventilation, and air conditioning) infrastructure. Prior to any construction at Mount Vernon, the team conducts archaeological research in order to learn about an area’s history and use over time.

A member of Mount Vernon's Archaeology team works in the North Grove. (MVLA)

What is the North Grove?

Mount Vernon's North Grove, as shown in an undated photograph. (MVLA)

In the mid-1770s, Washington undertook a massive building campaign during which the Mansion was expanded and new outbuildings built. Part of this effort involved implementing a new landscaping plan for the estate.

As the north wing of the Mansion (what would become the New Room) was under construction, Washington was called away to lead American forces in the Revolutionary War. Despite the distance, and the rigors of war, Washington remained heavily involved in the building efforts at Mount Vernon by way of letters to his cousin Lund Washington, who served as steward of the estate in Washington’s absence.

In these letters, Washington expressed his desire to plant trees of “locusts altogether” north of the Mansion, creating a landscaped grove of black locusts and underlying bushes. Intent on making the Mansion visible from all five of his farms, Washington was using trees to direct a viewer’s line of sight towards the Mansion. A native species, the black locust grows quickly—a trait that would have appealed to Washington, who was eager to establish a tree grove.

Visitors to Mount Vernon lounge in the North Grove, 1945. (MVLA)

The North Grove has largely remained a green space since Washington’s time. Over the decades, several generations of trees have come and gone, as well as tourists who have taken shelter in the grove’s shade.

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The North Grove Through Time

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Frequently Asked Questions

Why was excavation done in alternating squares?

The Archaeology team excavated 10-by-10-foot square units in a checkerboard pattern. (MVLA)

The Archaeology team excavated 10-by-10-foot square units in a checkerboard pattern. (MVLA)

Guided by a ground-penetrating radar survey conducted prior to excavation, the Archaeology team began opening 10-by-10-foot square units in a checkerboard pattern.

Archaeologists use this technique for a couple of reasons. As Mount Vernon Research Archaeologist Jason Boroughs explains, “By alternating these 10-foot squares, if there’s something linear that’s running across them—it could be a fence, a ditch, a former walkway—it will cross those units. By digging the alternating ones, we open up the maximum amount of area, and we can see what’s happening here, there, and everywhere in between. So it’s a way of guiding our discoveries and maintaining control over the area.” 

After digging a checkerboard pattern, the Archaeology team then excavated the remaining squares, thereby excavating the entire area.

What kinds of tools were used?

The archaeologist’s toolkit is a varied one. It ranges from the high-tech (devices such as ground-penetrating radar, satellite photography, GPS, and laser-equipped surveying and measuring equipment) to the tried-and-true (shovels, wheelbarrows, sifting screens, and the common masonry trowel).

A member of Mount Vernon's Archaeology team works in the North Grove with a masonry trowel. (MVLA)

How difficult was it to excavate around the trees in the North Grove? And did any trees need to be removed?

This excavation required working around the root systems of trees, as well as the removal of four trees. (MVLA)

This excavation required working around the root systems of trees, as well as the removal of four trees. (MVLA)

Using their variety of tools, Mount Vernon’s archaeologists are able to skillfully excavate the soil around and underneath a tree’s trunk, exposing a portion of its root system. The process can be challenging.

“It comes down to experience—the amount of years an archaeologist has spent doing this,” Boroughs explains. “Think of it like this: Blacksmiths train to create things out of metal. We’re actually in a similar line of work; I would consider ourselves like craftspeople or artisans. It’s just that we’re removing soil in a very specific way.”

Four black locust trees required removal from the North Grove, as they sat in the footprint of the bunker’s eventual construction. Despite their large size, the trees were only about 23 years old, having been planted after the construction of the original bunker in 1998 — a testament to the black locust’s rapid growth, which so attracted Washington to the species.

Unfortunately, none of Washington’s original black locust trees survive in the North Grove.

How far down do you dig?

After soil layers are analyzed and excavated, the soil is then sifted through 1/4-inch wire mesh in order to recover any artifacts present. (MVLA)

After soil layers are analyzed and excavated, the soil is then sifted through 1/4-inch wire mesh in order to recover any artifacts present. (MVLA)

As Boroughs explains, archaeologists read soil layers the way historians read the pages of a book. “Each human activity has impacted the ground in a certain way, and we’re trained at reading and interpreting what happened and when it happened.”

After soil layers are analyzed and excavated, the soil is then sifted through 1/4-inch wire mesh in order to recover any artifacts present. Soil samples occasionally undergo even more refined screenings (using 1/16-inch mesh), yielding minuscule artifacts such as eggshells, beads, straight pins , and even fish bones and scales.

Eventually, archaeologists reach a dense layer of clay called “subsoil,” containing no artifacts or evidence of human activity. It is here that they stop their excavations. Depending on the site, that might be anywhere from a few inches to several feet below the surface.

What happens when you find an artifact? How is it cataloged?

When an artifact is discovered, several points of information are recorded, including the square and soil layer in which it was found. “Where we find these objects is as important as the objects themselves,” explains Curator of Preservation Collections Lily Carhart, “and if we lose that context, we lose a big piece of the puzzle.”

Interns and volunteers then clean, sort, bag, and label each individual object before an archaeologist enters it into the Digital Archaeological Archive of Comparative Slavery (DAACS), a database that allows archaeologists to compare artifacts from sites of enslavement in the United States and the Caribbean.

Artifacts Discovered

A collection of artifacts from the North Grove, including an almost complete John Posey wine bottle seal, a projectile point with a stemmed base, an enamel twist wine glass stem, and a mid-20th-century lipstick tube which seems to have been hit with a tent spike or something similar. (MVLA)

A collection of artifacts from the North Grove, including an almost complete John Posey wine bottle seal, a projectile point with a stemmed base, an enamel twist wine glass stem, and a mid-20th-century lipstick tube which seems to have been hit with a tent spike or something similar. (MVLA)

Notable objects discovered during the excavation of the North Grove included:

  • Several lithic concentrations (sites where Native Americans were crafting stone tools), including 5 hearth-like stone scatters.
  • Pre-Colombian projectile points (arrowheads and spear points) dating primarily to the Middle Archaic period. At 3,500-5,500 years old, these artifacts are roughly as ancient as the pyramids.
  • A variety of 18th-century English, German, Chinese, and American ceramic tablewares and storage vessel fragments, as well as an “air-twist” wine glass stem (high-quality and fashionable tableware used by the Washington family).
  • 18th-century lead shot of assorted sizes (ammunition used in hunting or sport).
  • Remnants of a former walkway, likely dating from the late 19th and into the 20th centuries. Both ground-penetrating radar scans and historic photos indicate that the walkway led from the north lane to the north cellar entrance of the Mansion.
  • Objects associated with tourism, highlighting the importance of Mount Vernon as a touchstone of American identity: modern coins, photographic flash bulbs, children’s toys, and commemorative wine glass fragments were common finds.

Projectile Point

This point from the Late Archaic period was never completed, and the two fragments were found in adjacent units in the North Grove. Perhaps the person who made it got frustrated when it broke during production and threw the pieces down on either side of them.

Projectile Point

Rhyolite Lehigh / Koens-Crispin projectile point from the Late Archaic period. (MVLA)

This is the seventh John Posey seal to be excavated at Mount Vernon. John Posey was Washington’s neighbor whose property Washington eventually purchased around 1770, which became part of Union Farm. (MVLA)

This is the seventh John Posey seal to be excavated at Mount Vernon. John Posey was Washington’s neighbor whose property Washington eventually purchased around 1770, which became part of Union Farm. (MVLA)

A reproduction wine bottle with Augustine Washington’s seal alongside the wine bottle seals excavated on Mount Vernon property to date. The Posey wine bottle seal discovered in the North Grove is at the bottom right. (MVLA)

A reproduction wine bottle with Augustine Washington’s seal alongside the wine bottle seals excavated on Mount Vernon property to date. The Posey wine bottle seal discovered in the North Grove is at the bottom right. (MVLA)

John Posey Wine Bottle Seal

John Posey was Washington’s neighbor whose property Washington eventually purchased around 1770, which became part of Union Farm. A fellow veteran of the Virginia Regiment in the 1750s, Posey rode to the hounds with Washington, frequently visited Mount Vernon in the years prior to the Revolution, and was clearly a convivial companion. This is the seventh John Posey seal to be excavated at Mount Vernon, a larger number than the other seals located to date.

Wine bottle seals are one of the very few artifacts types that archaeologists can connect with specific people. They were created by adding a blob of glass to the shoulder or side of a wine bottle and then impressing it with a personalized stamp. These could be initials or coats of arms from individuals, tavernkeepers, or merchants and were used during the 17th and 18th centuries. Because of the extra glass needed for the seal and the custom-made stamp, bottles with seals were more expensive and served as a symbol of wealth.⁣
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The adjacent photo shows a reproduction wine bottle with Augustine Washington’s seal alongside the wine bottle seals excavated on Mount Vernon property to date. Our 19 seals come from George Washington’s neighbor John Posey; Martha Washington’s first husband, Daniel Parke Custis and his father, John Custis; George Washington’s father, Augustine Washington; the Fairfax family, and unidentified seals, including “HEE.”

The North Grove fragment held next to a surviving, intact Cincinnati Service plate. (MVLA)

The North Grove fragment held next to a surviving, intact Cincinnati Service plate. (MVLA)

This fragment discovered at Union Farm showcases a distinct decorative pattern that almost certainly indicates it as being from the Cincinnati Service. (MVLA)

This fragment discovered at Union Farm showcases a distinct decorative pattern that almost certainly indicates it as being from the Cincinnati Service. (MVLA)

Porcelain Fragment of Washington's Cincinnati Service

Archaeologists can't always pinpoint the exact year of purchase of an excavated ceramic fragment, so the archaeology lab crew was very excited when they connected this recently excavated ceramic fragment from the North Grove with one of the most iconic porcelain sets acquired by George Washington in 1786—the Cincinnati Service.⁣
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The only other porcelain fragment of the same service excavated from Mount Vernon was found at Union Farm. This fragment of Chinese export porcelain showcases a distinct decorative pattern (circled in red on the photograph) that almost certainly indicates it as being from Washington’s prominent Cincinnati Service.

Learn More About the Cincinnati Service

"Large Cent" Copper Coins

Two "large cent" copper coins represent multiple generations of Washington households. (MVLA)

Two "large cent" copper coins represent multiple generations of Washington households. (MVLA)

Mount Vernon’s archaeologists love finding coins because they help assign dates for other artifacts and soil layers found in the same area.

Objects found in layers below generally pre-date, and items above typically post-date the coin’s deposition. Two “large cent” copper coins—dated 1798 and 1817—recovered adjacent to the Mansion’s north gabled end represent multiple generations of Washington households.

The coins were the first series of one-cent pieces issued by the newly chartered United States Mint in Philadelphia.

U.S. Army Artillery Corps Button

This copper alloy button was among the first series of U.S. military regalia to feature an American eagle.⁣ ⁣(MVLA)

This copper alloy button was among the first series of U.S. military regalia to feature an American eagle.⁣ ⁣(MVLA)

Since the close of the Revolutionary War, Mount Vernon has welcomed generations of American servicemen and women. ⁣
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This U.S. Army Artillery Corps button, issued during the War of 1812, was in active service between 1814-1821. The copper alloy button was among the first series of U.S. military regalia to feature an American eagle.⁣

Mineral Water Bottle Fragment

Imported mineral water bottle fragments are found on many historical, archaeological sites. (MVLA)

Imported mineral water bottle fragments are found on many historical, archaeological sites. (MVLA)

General fascination with artisanal waters is not a recent phenomenon.⁣

Imported mineral water bottle fragments are found on many historical, archaeological sites, like this example. This fragment likely represents a late 19th-century Cantrell and Cochrane mineral water bottle manufactured in the Cromac area of Belfast, Northern Ireland.

Bottles like this were often sold at ports and apothecaries as they were thought to contain health benefits. Common 19th-century cures encouraged those with certain ailments to bathe in health spas located in natural springs. Such health beliefs may have encouraged individuals to purchase bottled spring water.

Tab Badges

This badge likely post-dates the Kennedy Center’s 1971 opening. (MVLA)

This badge likely post-dates the Kennedy Center’s 1971 opening. (MVLA)

Metal fold tab badges are common ephemera from museums and political campaigns. These badges came from two different units during the excavation.

The white badge reads “Friends of the Kennedy Center” and likely post-dates the Kennedy Center’s 1971 opening.

The green badge is from the Museum of the American Revolution in Philadelphia, which began using the badges around 2018. Artifacts like these give us more insight into the many visitors who come to Mount Vernon each year.⁣

War Nickel

“War nickels” were made from an alloy of copper, silver, and manganese instead of the usual copper and nickel in order to conserve nickel for the war effort during WWII. ⁣(MVLA)

“War nickels” were made from an alloy of copper, silver, and manganese instead of the usual copper and nickel in order to conserve nickel for the war effort during WWII. ⁣(MVLA)

Minted between 1942 through 1945, “war nickels” were made from an alloy of copper, silver, and manganese instead of the usual copper and nickel in order to conserve nickel for the war effort during WWII. ⁣
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Along with this nickel, dozens of other artifacts were recovered from the backfill of a modern irrigation line trench. There were 18th-century ceramic and glass fragments, wrought nails, a 1958 wheat penny, a 1972 quarter, and over 80 other modern artifacts, including food and beverage packaging fragments, a dental flosser from 2006, and flashbulbs. ⁣
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While all the soil layers where these artifacts were originally deposited were disturbed by the installation of the irrigation line, we can still learn about the history of the North Grove by studying all these artifacts together.⁣

Lipstick Tube

This mystery lipstick was found by Mount Vernon archaeologists during the North Grove excavations. ⁣(MVLA)

This mystery lipstick was found by Mount Vernon archaeologists during the North Grove excavations. ⁣(MVLA)

The tube is made of copper alloy with a pattern of vertical stripes. There are no identifying manufacturer marks, but this tube is similar to others made in the mid-20th century. Surviving dark red-pink lipstick is still visible through the hole in the side. ⁣
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Due to the North Grove’s location next to the east lawn, we believe this lipstick was punctured by a tent stake from one of the many events Mount Vernon has hosted on the lawn over the years.⁣

Sunkist Soda Can

Crushed Sunkist soda can (c. 1990-1998). (MVLA)

Crushed Sunkist soda can (c. 1990-1998). (MVLA)

The modern artifacts we excavate can tell stories just as vivid as the historic artifacts. ⁣
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While cataloging artifacts from a modern planting feature from the North Grove excavation, our archaeologists identified two datable modern artifacts—a crushed Sunkist soda can (c. 1990-1998) and a partial Baby Ruth candy bar wrapper (c. 1988-1997). ⁣
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In the 1990s, Mount Vernon archaeologists monitored over 20 trees and shrubs being planted in the North Grove. Perhaps whoever planted the tree in this particular hole had a snack break and tossed their trash in the hole as they backfilled it.

More North Grove Artifacts

Explore a selection of fascinating artifacts uncovered just north of the Mansion by Mount Vernon's Archaeology team.

Were some of these artifacts from a previous excavation?

Objects associated with tourism highlight the importance of Mount Vernon as a touchstone of American identity. Pictured here is an unused flashbulb from 1965 - 1980s, discovered in the North Grove. (MVLA)

Objects associated with tourism highlight the importance of Mount Vernon as a touchstone of American identity. Pictured here is an unused flashbulb from 1965 - 1980s, discovered in the North Grove. (MVLA)

Yes, members of the Archaeology team have been at work cataloging thousands of artifacts recovered during the 1998 North Grove excavation, which was executed prior to the construction of the existing HVAC bunker.

“The idea is to study the entire area together,” Carhart explains. “In 1998, the artifacts would’ve been cataloged in a different database, and less information about each object was recorded. As time has progressed, our computing power has increased, and the questions we’re asking of these materials have changed. In order to understand the full picture of the North Grove, we need to catalog the 1998 artifacts to the modern standard.”

Jaw Harp

This jaw harp was identified from a bag full of nails during a recent re-examination and cataloging of the artifacts from a 1998 excavation in the North Grove. (MVLA)

This jaw harp was identified from a bag full of nails during a recent re-examination and cataloging of the artifacts from a 1998 excavation in the North Grove. (MVLA)

Jaw harps, like the one pictured, were popular amongst European colonialists and enslaved Africans in America as musical instruments/trade items and are commonly excavated from North American historic archaeological sites. ⁣
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Originating from Asia thousands of years ago, jaw harps have been played across cultures and continents. To this day, the jaw harp is a popular component in American folk music. Mount Vernon’s Archaeology Department has identified a total of four jaw harps. However, the one shown here is unique as it is the only one that was hand-forged iron rather than cast copper alloy.⁣
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This jaw harp was identified from a bag full of nails during a recent re-examination and cataloging of the artifacts from the 1998 excavation in the North Grove. This underscores the importance of returning to legacy collections and that archaeological discoveries go far beyond just excavation. ⁣

Learn More About Jaw Harps

How has this dig contributed to the way you interpret the North Grove?

An In-Depth Look

As Mount Vernon's Mansion Revitalization Project proceeds into 2026, take a deep dive into the various aspects of this landmark preservation project.

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