[2][3] Pollepel is a Dutch word meaning "(pot) ladle" The island is about 50 miles (80 km) north of New York City[4] and about 1,000 feet (300 m) from the Hudson River's eastern bank.

[8] In 1867 the business occupied a ship chandlery on Atlantic Avenue engaged in the purchase of worn rope for papermaking.

[2][9] Bannerman's illustrated mail order catalog expanded to 300 pages; and later became a reference for collectors of antique military equipment.

[10] Because his storeroom in New York City was not large enough to provide a safe location to store thirty million surplus munitions cartridges,[8] in the spring of 1901 he began to build an arsenal on Pollepel.

In 1917, following the American entry into World War I, Bannerman sold a number of these weapons to the US Army, which intended to mount them on new carriages as field guns for the Western Front.

Bannerman's sales of military weapons to civilians declined during the early 20th century as a result of state and federal legislation.

[4] The island and buildings were bought by New York State in 1967, which took possession after the old military merchandise had been removed, and the relics given to the Smithsonian.

In the 21st century, the castle is the property of the New York State Office of Parks, Recreation and Historic Preservation and is mostly in ruins.

[18][19][20][21] On June 28, 2015, the public art piece Constellation by Beacon-based artist Melissa McGill debuted on and around the castle ruins.

The work consists of seventeen LEDs mounted on metal poles of varying heights, which when lighted for two hours each night are intended to create the appearance of a new constellation.

The main characters in Adventures of a Cat-Whiskered Girl by Daniel Pinkwater (2010), set in the 1950s, visit Pollepel Island and hang out with a family of trolls who are squatting in the abandoned castle.

[26] The novel The Devils That Haunt You (ebook 2016 and paperback 2018) by Rick Hoffman, takes place in part on Pollepel Island and features a fictionalized account of its construction and history.