(NEW YORK) — The New York City bomb squad was sent out to defuse history Thursday morning when summoned to assess the danger from a 350 pound Civil War cannonball 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. During the Revolutionary War, the British housed captured American soldiers on prison ships at the island where the ominously named Execution Light marks the southern end.
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 — and coastal fortifications — often turned the tide.
The former military base on Governor’s Island is currently the site of excavation as part of a cleanup of park land. Workers found the cannonball while moving piles of rocks.
Copyright 2012 ABC News Radio
Ariane de Vogue and Laura Jarrett, CNN
Sara Stewart, CNN
Eliza Mackintosh, CNN