New Castle is a town in Rockingham County, New Hampshire, United States. The population was 968 at the 2010 census. The smallest town in New Hampshire, and the only one located entirely on islands, it is home to Fort Constitution Historic Site, Fort Stark Historic Site, and the New Castle Common, a 31-acre (13 ha) recreation area on the Atlantic Ocean. New Castle is also home to a United States Coast Guard station, as well as the historic Wentworth by the Sea hotel. The main island on which the town sits is the largest of several at the mouth of the Piscataqua River and was originally called Great Island. Settled in 1623, an earthwork defense was built on Fort Point which would evolve into Fort William and Mary (rebuilt in 1808 as Fort Constitution). Chartered in 1679 as a parish of Portsmouth, it was incorporated in 1693 and named New Castle after the fort. Until 1719 it included Rye, then called Sandy Beach. The principal industries were trade, tavern-keeping and fishing. There was also agriculture, using the abundant seaweed as fertilizer. Fort William and Mary was the site of one of the first acts of the American Revolution. On December 14, 1774, colonists arrived at midnight aboard a gundalow (sailing barge), waded ashore and climbed over the fort's wall. Captain John Cochran and the fort's five soldiers surrendered, whereupon the rebels loaded onto the boat 100 barrels of gunpowder. As a gesture of chivalry, they returned to Cochran his swordwith which he then lunged at them. Nevertheless, the boat was rowed up the Piscataqua River to Durham, where the ammunition was stored in the cellar of the Congregational Church. The next day, the colonists returned to the fort and removed 15 of the lighter cannon and all small arms. The gunpowder was used at the 1775 Battle of Bunker Hill.