Inside Bannerman Castle, The Abandoned 20th-Century Arsenal Located Just North Of New York City

Published March 10, 2024

Built by an eccentric arms dealer on the isolated Pollepel Island, the Scottish-influenced Bannerman Castle looks like something out of a fairytale — but it has a spooky mythology all its own.

About 60 miles north of New York City, on the supposedly haunted shores of Pollepel Island in the Hudson River, sits the ruins of a 20th-century fortress known as Bannerman Castle. Originally built in the early 1900s as an army surplus arsenal, the castle was abandoned after it was damaged in a series of fires and explosions.

Bannerman In The Fall
Aerial Bannerman Island
Arsenal Building Sign
Banneman Arches
Inside Bannerman Castle, The Abandoned 20th-Century Arsenal Located Just North Of New York City
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Francis Bannerman, the eccentric weapons tycoon who built the castle, was not your average arms dealer. A first-generation Brooklynite of Scottish descent, he was a pacifist who regarded his vast military collection a tribute to the lost art of weapon making. However, his castle and its grounds would prove to be his greater legacy.

Originally based in Manhattan, Bannerman's business — and vast supply of flammable black powder — grew so large that the city of New York forced him to move out. His son discovered Pollepel Island while out canoeing on the Hudson, and Bannerman purchased it in 1900 to build a huge arsenal to store his weapons stock.

From there, he brought the baronial, Scottish-inspired Bannerman Castle into existence.

The Construction Of Francis Bannerman's Architectural Oddity

Francis Bannerman was not an architect. That's what makes the Gaudi-esque character of the castle and its accompanying buildings so astounding. Rather than work with professional architects, Bannerman designed the castle almost entirely by himself, often drawing up plans on the backs of napkins and envelopes to create the estate in the style of a Scottish fortress.

When Bannerman Castle was nearly finished, barges ferried cannons and artillery up the river for storage. But Bannerman and his wife Helen decided to keep building. They designed an additional castle to serve as a family summer residence, complete with lovely gardens, a dock, a moat, and even an outhouse built for two.

The Bannermans landscaped the gardens themselves, importing soil, digging winding pathways around the island, and building the garden walls. Helen Bannerman enhanced the terraces with plants, flowers, and shrubs — some of which are still alive today.

With Scottish, Moorish, and Belgian design influences, the castle was alive with intricate stone and brickwork. Everything was elaborately adorned with thoughtful details. Bannerman even had the name "Bannerman's Island Arsenal" emblazoned on its façade.

"There is no way to describe something so eccentric," said Thom Johnson, vice-president of the Bannerman Trust, according to the non-profit Historic Hudson River Towns. "Look at the north view — there's no right angles on these buildings! Look at all these textures, all that he did with masonry. It's a piece of sculpture! The style is almost gaudy, but somehow he manages to pull it off. Bannerman knew exactly what he was doing, and he did it his own way."

The Haunted History Of Pollepel Island

Before Bannerman Castle, Pollepel Island had a spooky history all its own. The portion of the river surrounding the island had a reputation for violent storms and howling winds. According to local Hudson Valley legend, Dutch sailors in the 17th and 18th centuries attributed these storms to a sinister Goblin king who resided on the island.

The sailors named this being the "Heer of Dunderberg" — "Heer" meaning King, "dunder" meaning thunder, and "berg" meaning mountain. The Heer of Dunderberg was said to rule an army of imps, and had the power to summon the violent storms that wreaked havoc on passing ships.

Bannerman Castle

Susan Candelario/Alamy Stock PhotoPollepel Island is said to haunted by a sinister goblin king named Heer of Dunderberg.

According to believers, during these infamous squalls, you can still hear the captain of the ghost ship The Flying Dutchman barking orders to his crew.

However, it's possible that this "folk legend" was invented by Washington Irving, author of The Legend of Sleepy Hollow. Irving's literary success is due in part to his knack for writing tales of lore that sound like they could be true — and he detailed the legend of the Heer of Dunderberg in his 1822 short story "The Storm-Ship."

Bannerman Castle Falls To Ruin

Unfortunately, Bannerman Castle has seen its share of catastrophe.

In 1918, Frank Bannerman died before the castle was 100 percent complete. Then, in 1920, the arsenal's powder house exploded, lending credence to New York City's decision to boot Bannerman from city limits.

"The explosion was heard from Poughkeepsie to Peekskill," Steve Santangelo, a tour guide at the castle, said to the New York Times. And 6sqft reports that about 200 tons of shells and powder were involved in the blast.

The explosion damaged the castle, shattering the windows and jettisoning part of the tower into the river. The Bannerman family, narrowly escaping death, remained in the residence until about 1930. That's when the castle began crumbling.

Bannerman Castle Wall

Wikimedia CommonsBannerman Castle was abandoned after a series of fires and explosions damaged it.

In 1967, the Bannerman family sold the island to New York State; two years later, it's suspected that an arsonist set the mysterious fire that reduced the castle to ruins.

Eerily, seven years before the blaze, Frank's grandson Charles had written prophetically: "No one can tell what associations and incidents will involve the island in the future. Time, the elements, and maybe even the goblins of the island will take their toll of some of the turrets and towers, and perhaps eventually the castle itself."

Visiting Bannerman Castle Today

Farm To Table Dinner

Bannerman CastleToday, visitors to Pollepel Island can enjoy farm-to-table dinners and outdoor movies on the castle grounds.

For years, New York banned visitors from Pollepel Island because it was too dangerous. That didn't stop people from illegally visiting and photographing the abandoned castle. Poison ivy ran rampant and snakes infested the grounds, but visitors still braved these hazards — and the choppy waters of the Hudson River — for a glimpse of the crumbling historic ruin.

However, this was not the end of Bannerman Castle's story. In 1992, a Hudson Valley local named Neil Caplan founded the Bannerman Castle Trust, which has raised funds to stabilize the castle ruins, clear overgrown pathways, and revitalize the landscaping.

Today, Bannerman Castle is a haven for enjoying cultural events. Tours of the grounds run from April through October and include the boat ride over to the island. The Bannerman Castle Trust also hosts horror movie nights, theater performances, kayak tours, and farm-to-table dinner events. Last year, in an exclusive dining experience, the Trust even recreated an 11-course, first-class dinner that was served on the Titanic.

Over 100 years after Bannerman Castle was built, the historic Hudson Valley landmark is now closer to a museum than a bomb site. We can only assume that's what Francis Bannerman would have preferred.

After exploring Bannerman Castle, read about the other enchanting castles of New York and the American royalty that built them. Then, explore the abandoned New York City quarantine site that no one's allowed to visit.

Erin Kelly
An All That's Interesting writer since 2013, Erin Kelly focuses on historic places, natural wonders, environmental issues, and the world of science. Her work has also been featured in Smithsonian and she's designed several book covers in her career as a graphic artist.
Jaclyn Anglis
Jaclyn is the senior managing editor at All That's Interesting. She holds a Master's degree in journalism from the City University of New York and a Bachelor's degree in English writing and history (double major) from DePauw University. She is interested in American history, true crime, modern history, pop culture, and science.
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Kelly, Erin. "Inside Bannerman Castle, The Abandoned 20th-Century Arsenal Located Just North Of New York City.", March 10, 2024, Accessed June 24, 2024.