▁south ▁of ▁the ▁island ▁in ▁the ▁hope ▁of ▁containing ▁the ▁British ▁further ▁down stream . ▁The ▁earth works ▁at ▁Fort ▁Constitution ▁were ▁un fin ished ▁when ▁British ▁troops ▁destroyed ▁them ▁in ▁ 1 7 7 7 . ▁ ▁In ▁ 1 7 7 8 ▁Polish ▁engineer ▁Th ad de us ▁Kos cius ko ▁began ▁design ing ▁Fort ress ▁West ▁Point ▁as ▁a ▁series ▁of ▁for ts ▁and ▁red ou b ts ▁on ▁both ▁sides ▁of ▁the ▁river . ▁On ▁Constitution ▁Island , ▁a ▁bar ra cks , ▁three ▁red ou b ts , ▁and ▁a ▁water ▁battery ▁were ▁constructed . ▁ ▁Ch ain ▁The ▁island ▁is ▁perhaps ▁best ▁known ▁as ▁the ▁eastern ▁anchor - point ▁for ▁the ▁Great ▁Ch ain , ▁a ▁massive ▁iron ▁structure ▁that ▁stretch ed ▁across ▁the ▁narrow ▁b end ▁in ▁the ▁Hudson ▁between ▁the ▁island ▁and ▁the ▁main land ▁at ▁West ▁Point . ▁The ▁chain ▁was ▁intended ▁to ▁prevent ▁British ▁naval ▁vessels ▁from ▁navig ating ▁freely ▁along ▁the ▁Hudson . ▁This ▁was ▁the ▁second ▁attempt ▁to ▁string ▁a ▁chain ▁across ▁the ▁Hudson ▁River ▁in ▁an ▁effort ▁to ▁prevent ▁the ▁British ▁from ▁taking ▁control ▁of ▁the ▁Hudson ▁thereby ▁splitting ▁the ▁American ▁colon ies . ▁The ▁first ▁chain , ▁which ▁we ighed ▁ 3 5 ▁tons ▁and ▁was ▁ 1 6 5 0 ▁yards ▁long ▁stretch ed ▁between ▁the ▁base ▁of ▁Fort ▁Mont gom ery ▁and ▁the ▁rock ▁at ▁Anthony ' s ▁N ose . ▁That ▁chain ▁failed ▁to ▁stop ▁the ▁British ▁forces ▁when ▁they ▁attacked ▁Fort s ▁Mont gom ery