Constitution island divides the bed of the Hudson unequally at the bend round the point, the western branch being a marshy shallow. This island, a mass of rock, was defended by batteries on a level with the water, and the glacis formed in the rock bade defiance to trenches. A heavy chain cramped into the rocks at either end, supported by buoys, stretched across the angle made by the river, and formed an effectual bar. This chain prevented the English from ascending the river in their armed ships, and the great object of the works on both sides was to protect it. Twenty pieces of heavy ordnance, discharging grape, menaced those who should attempt to cut a link, with destruction. And the roller on which the chain moved, suffered it to grow slack, thereby preventing any iron-beaked vessel from breaking it under the combined forces of wind and tide. As soon as the shock was thus broken, the chain could be immediately made tense, and the vessel must be turned aside and stranded on one or the other shore.
There were two chains created and strung across the Hudson River in an effort to prevent the British from taking control of the Hudson thereby splitting the American colonies. The first chain, which weighed 35 tons and was 1650 yards long stretched between the base of Fort Montgomery and the rock at Anthony's Nose. That chain failed to stop the British forces when they attacked Forts Montgomery and Clinton. That chain was dismantled by the British.
The second chain was laid across the Hudson between Constitution Island and West Point. Each link was two feet long and weighed 180 pounds. This chain was never tested in its effectiveness against British ships. The focus of the war shifted to other battle grounds and they never again tried to bring their ships this far up the Hudson.