Pollepel Island was discovered by the Europeans during the first navigation of the Hudson River by early Dutch settlers in the Province of New York, at the Northern Gate of the Hudson Highlands. During the Revolutionary War, patriots attempted to prevent the British from passing upriver by emplacing 106 chevaux de frise (upright logs tipped with iron points) between the island and Plum Point across the river (see Hudson River Chains). Caissons from several chevaux de frise still rest at the river bottom. Still, these obstructions did not stop a British flotilla from burning Kingston in 1777. General George Washington later signed a plan to use the island as a military prison; however, there is no evidence that a prison was ever built there.