Long before Pollepel Island was purchased, early settlers seeking to hide from the local indigenous people sought refuge on the island because the indigenous regarded it as an abode of evil spirits.
In was in 1900 that Bannernan Island was purchased to store millions of munition cartridges outside where they were being stored in NYC. The Scottish-born civilian owner, Francis Bannerman VI, designed this structure to resemble a castle, a homage to his heritage. After the Spanish-American War, Bannerman purchased 90% of military surplus, and this is where he stored it all. The island was ideal because it was only accessed by boat and the Hudson River acted as a natural moat to protect the dangerous goods inside.
In 1920, a powder house on the island exploded, causing damage that was never repaired. The business continued to decline and by the 1950s, the island was put up for sale after the ferry that supplied the island sunk. In 1969, a fire that burned for 3 days destroyed most the interior of the Bannerman Castle and by 2009, a large section of the walls collapsed. Today, the castle is property of the New York State Office of Parks, Recreation and Historic Preservation and is mostly in ruins.