Ask around South Baltimore and you’ll hear that Federal Hill is hollow. Pirates hid their loot inside it and Union soldiers stored their ammunition in it. A secret passage, the story goes, runs from the hill all the way to Fort McHenry.
The tunnels are real, but the legends mostly aren’t. What’s actually under the hill is a maze of hand-dug sand mines, plus a few brewery vaults dug alongside them. Newspapers of the day said the sand supplied Baltimore’s glass factories.
For well over a century, those old diggings have kept opening up underfoot. The hill is the park on the south side of the Inner Harbor, and the caves keep turning up on the streets around it.
The legends
When the Baltimore Sun asked longtime residents about the caves in December 1911, this is what it heard:
Weird and varying tales are told by the older residents of South Baltimore regarding the origin of the caverns. These embrace stories of treacherous pirates who were wont to use them as hiding places for their ill-gotten treasures; of the early settlers of Baltimore who fled into their depths when hostile Indians threatened attack, and of Civil War days, when the Federal troops planted their guns on the summit of Federal Hill and stored their ammunition in the caves.
The Civil War version kept coming back. In 1927, the Sun found one faction of neighbors insisting, “Old Ben Butler built them during the Civil War.”
In 1951 houses on East Clement Street started sinking. “Some of the oldtimers thought it was part of a century-old tunnel that once ran from Fort McHenry to Federal Hill,” the paper reported. A year later, in 1952, a city parks superintendent blamed a new hole in the hill on tunneling by Union troops.
Even the hill’s 1969 historic district nomination to the National Register of Historic Places repeated the lore. It says that during the War of 1812 “intensive digging was begun for a tunnel” from Commodore Joshua Barney’s wharf into the north side of the hill. According to the form, Barney stored munitions in it.
The same form says Union troops enlarged the tunnels into a route to Camden Station. We haven’t found a record from either war that backs any of it up.
A “mysterious cavern” in 1838
The earliest account we’ve found ran on the front page of the Sun on March 3, 1838, in a letter headed “Mysterious Cavern.” The writer said he’d been walking near Federal Hill “with a scientific friend” when they spotted the mouth of a cave. The frost had apparently exposed it by loosening the bank.
The entrance or mouth of the cavern is about half way up the steep bank directly back of the glass-house. With considerable difficulty, I managed to climb up to it, and when my eye surveyed the spacious interior, I am at a loss to say whether my feelings were those of awe or delight. Immediately beyond the mouth the cavern widens into a chamber about fifteen feet wide and thirty long, with a smooth level floor, and a roof about ten or twelve feet in height.
After a learned paragraph on iron stone and yellow ochre, the writer credits a theory to “Count Schwarmendorf.” He was supposedly an attaché at the Russian embassy in Greece. The cave, he says, “has evidently been formed by the same animal called by the Grecians ‘Psammopherontes.'”
This animal’s habits induce it to prefer the level ground, and it removes the choice veins of sand found breaking from the sides of the hills in small portions, and this fine sand after removal, is used in the habitation of its tribe on the lower ground.
We couldn’t find any record of a Count Schwarmendorf, but the animal’s name is a clue. In Greek, psammos means sand and pherontes means “carrying.” A creature that hauls sand off the hillside to build homes on the low ground sounds a lot like the people of Baltimore.
The hill that was being dug away
Notice that the glass-house sat below the cave. When a Sun reporter toured Federal Hill in September 1846, he found it being dug away.
“Alas! for the green sides and grassy slopes, of which it once could boast,” he wrote. “Black smoke and never hushing steam engines now usurp their place, and the pick and the spade have spoiled the beautiful face that Nature originally endowed it with.”
“Manufactories, foundaries, furnaces, potteries, glassworks, and a host of others, come in for their share of this hill,” the Sun reported. On the north side, the reporter stopped at “the terrible chasm of near forty feet” that Hughes Street had cut into the hill. “From this face of the hill is obtained the silex,” or silica, “which supplies these works,” the glass factories across the street.
Ben Butler’s cave
The Butler legend starts on the stormy night of May 13, 1861. That’s when Gen. Benjamin F. Butler marched Union troops onto Federal Hill and took control of Baltimore.
By his own account in his 1892 memoir, Butler’s Book, he set up in a little German tavern at the top of the hill. A Captain Farmer of Lowell soon came to him with a lantern.
“General, I have been informed that this hill is mined and we shall all be blown up.”
“Well, Captain,” said I, “there will be one comfort in that; we shall at least get dry. But I will go with you and reconnoitre.”
We went down under the hill and examined the place, and we found that the hill had been mined, and that a deep cave, which we explored, had been dug under it.
At the far end, Butler wrote, they found the miners’ tools. Those showed that the hill had been dug “for the very peaceable and proper purpose of getting sand.”
So the general who supposedly built the tunnels said he found a sand mine. Later in 1861 the 5th New York Zouaves arrived and built the earthwork fort that crowned the hill for the rest of the war.
The city’s own park board took on the Butler theory in 1927. “Some old residents attribute the tunnels to General Butler,” its history of Federal Hill Park said.
The history went on: “They say he intended to blow it up if taken from him.” But the board pointed out that in his autobiography Butler described the cave as nothing more than a sand pit.
A park on top of the caves
The city made the hill a public park around 1880, and the caves were trouble from the start. According to the park board, “Excavations for the wall uncovered caves, thought at the time to be sand pits.” The slopes bulged and slid for decades afterward, and the city drove piles into them in 1889 and again in 1905.
Boys with lanterns
By the turn of the 20th century, the old mines were a neighborhood playground. On Friday, April 3, 1903, a sealed cave entrance was reopened on a vacant lot at Battery Avenue and Church Street. The lot was on the west side of the park, and the Sun reported the entrance had been closed for seven years.
A great number of persons, with small boys in the majority, explored the cave yesterday and Friday, and in the evening many of the curious carried lanterns into the depths and sat and walked about there.
“It is said,” the Sun added, that one John Cupp had dug there years before. What he wanted, by that account, was “a fine quality of silver sand, which runs in veins about 35 or 40 feet below the surface of the ground.” The rooms, the paper said, were big enough “for a two-horse team to turn around.”
About the same time, the paper said, the owner of Rossmarck’s brewery at the foot of Cross Street dug north toward the hill. He was looking for a place to store casks and barrels, and the two excavations met. The lot had a new owner, and the plan was to wall the cave off and fill it in.
The cave-in of 1911
Eight years later, on December 26, 1911, the sidewalk at that same corner caved in. The Sun reported “a hole, 4 feet in diameter, leading to a cavern large enough to hold a good-sized moving van.”
The paper said the passages it opened were “veins of sand which had been followed out by diggers of Baker’s glass factory between 1840 and 1850.” William W. White, 70, who had played in the caves as a boy, said the diggings once ran from Covington Street to William Street.
White also remembered the brewery. A few years before the Civil War, he said, the Rossmarck Brewery stored beer in one of the main caves.
The cave opened at the foot of the hill on Covington Street near Montgomery Street. One Sunday a crowd of boys got in.
“That day South Baltimore enjoyed free beer,” White said. “Boys 10 years old were seen on the street intoxicated, and some persons carried away quantities of it in wagons.” How crazy is this?
A week after the cave-in, James W. Ogier of the City Engineer’s office crawled in through an opening no more than three feet high. He found a dome-shaped roof “marked with the picks wielded, perhaps, half a century ago by laborers in search of sand to use in making glass.”
The main tunnel ran about 75 feet in a rough crescent and was about seven feet wide. Seven short spurs branched off where the diggers had followed veins of white sand. Photographers came along, but they didn’t take any pictures, “for fear that the detonation of the flashlight might bring down a landslide.”
Up on the curb, a crowd of boys watched. One old man standing by the entrance talked to the paper. “I remember that when I was a boy we children used to play ‘hide-and-seek’ in the passages some of which were quite a distance from here.”
A labyrinth on Cross Street
Early in 1927, the United States Printing and Lithographing Company started a new building at Cross Street and Key Highway. The excavation revealed that the tunnels there were far more extensive than anyone thought.
The Sun described “the labyrinth of tunnels which radiate in every direction from a central stone-vaulted cavern.” One passage ran more than two blocks toward Federal Hill.
“Nothing but old beer vaults,” said one faction of neighbors, while the other blamed Butler. The park board split the difference. It suggested that probably the old diggings “in following up veins of particularly valuable potters’ clay and paint pigments were improved and made use of by the breweries.”
The Clement Street caverns
On Sunday, June 10, 1951, houses in the 600 block of East Clement Street began to crack. Five families, “totaling 30 men, women and children,” left the rowhouses from 606 to 614 East Clement, the Sun reported. Police had warned they would “risk death or injury” if they stayed.
At 608, Mrs. Joseph Brokos went down to her cellar and found a hole about 15 feet deep where part of her floor had been. That July, deputy highways engineer William L. Chilcote reported arched caverns dug in sand, with pick marks on the walls.
The roof was about 24 feet below the street, though the South Baltimore Peninsula Post gives about 30 feet. Chilcote put it this way:
“Based on our findings, it is our opinion that these caverns were made about 75 to 100 years ago for the purpose of mining a very fine grade of white sand.”
According to the Peninsula Post, the city filled the caverns later that year. It also tore down six houses on the block.
Less than a year later, on April 4, 1952, a hole 40 to 50 feet deep opened on the east side of Federal Hill Park. That side of the park overlooks Key Highway.
Caretaker Lawrence Quinn had noticed a dip in the ground that morning and jumped up and down on it. Nothing happened, and two hours later a Southern High School student ran up to tell him “there’s a big hole over there.”
“There are tunnels all under Federal Hill,” Harry W. Kues of the Parks Department told the Sun. “We have had some small depressions (in the earth) before but this is the worst we’ve ever had.”
The mine inside the hill
In 1992 the city began a $900,000 project to stop the frequent cave-ins and erosion on the hillside. On June 3, 1992, workers found a narrow entrance about halfway up the north slope. Behind it were more than 200 feet of white-walled tunnels.
It was a 19th-century commercial sand mine, and researchers speculated the sand went into high-quality glassware. The arched passages ran 20 to 30 feet below the top of the park and stood about 12 feet high.
There was a “big room” nearly 55 feet long. “The sand was very white and fine,” said Louise F. Akerson, archaeological curator at the Baltimore City Life Museums. “Workers used hand picks to get it out.”
Dan Ogle, superintendent for the contractor, Potts and Callahan, told the Sun’s Jacques Kelly, “We even found the places on the wall where they put candles. The fire smudges were still on the wall.” Someone had carved “Zimmerman” into the hardened sand, with “Balto.” underneath.
The archaeologists found a shard of mid-19th-century pottery and no evidence of Civil War materials. The crew sealed the entrances with 2,800 sandbags and left the main tunnel undisturbed inside the hill. As far as anyone knows, it’s still there.
Still down there
In April 2024, after a heavy rain, a tree on the empty city lot on East Clement Street sank about a foot. Cracks started showing up in the house next door. The Peninsula Post reported that city contractors drilled test borings up to 40 feet deep on the block in November 2025.
So there are tunnels under Federal Hill, but they weren’t dug by pirates or by Ben Butler. Most were dug by workers with picks and candles, following veins of fine white sand into the hill. Some were dug or taken over by brewers who wanted a cool place to keep their beer.
The letter writer of 1838 was onto something after all. The creatures hauling sand out of Federal Hill were real, and they were the people of Baltimore.
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