The New York City bomb squad was sent out to defuse history this morning when summoned to assess the danger from a 350 pound Civil War cannon ball found by workers excavating near a fort at the mouth of the East River whose batteries once protected Manhattan from an attack .
The cannonball is about 15 inches in diameter and appears to be solid.
The fort on Governor's Island is in the middle of the river that flows in and out of New York Harbor. It was first built by the fledgling Continental Army in 1776 and fired on British ships before being captured.
The Governor's Island fort is one of a network of forts that were built at the harbor entrance and near the East River and the Hudson to protect New York during colonial and post colonial wars where sea power often turned the tide.
The former military base on Governor's Island is currently the site of excavation as part of a clean up of park land. Workers found the cannon ball while moving piles of rocks.
Fire trucks, Emergency Service Units and the Bomb Squad - which last year defused a car bomb in Times Square - were ferried across from Manhattan to the island, which is more often the destination of urban walkers and tourists.