Fort Constitution, New Hampshire, by Alexius Horatius, Wikipedia.
Fort Constitution, located in New Castle, New Hampshire, overlooks the Piscataqua River and the Atlantic Ocean. Known as “The Castle” and “Fort William and Mary, before it was renamed Fort Constitution, it was first fortified sometime in 1631 and continued operating through the 1950s. Today, it is a National Historic Site and a New Hampshire State Park.
Located on a peninsula on the northeast corner of New Castle Island, the site was first fortified by the British in 1631. The fort was initially known as “The Castle” and guarded access to the harbor at Portsmouth, and served as the colony’s main munitions depot. It also protected Kittery, Maine, on the opposite shore, which the tribes of the Wabanaki Confederacy raided numerous times during the French and Indian Wars. It was manned by soldiers of the Province of New Hampshire who reported directly to the royal governor. The first installation was an earthwork fort with four large guns. A timber blockhouse was built in 1666.
Fort William and Mary, New Hampshire, 1705.
The earliest forts were built to protect the colonists, and the Castle was one of seven forts built to protect Portsmouth Harbor. The others included Forts Stark, Washington, and Dearborn in New Hampshire, as well as Forts Sullivan, McClary, and Foster in Maine.
The post was renamed Fort William and Mary around 1692, after the accession of William III and Mary II to the British throne. By this time, stronger defenses were required, and additional cannons and military supplies were sent from England. A breastwork was also constructed to protect them.
The first harbor light was installed at the site in April 1771; it consisted of only a lantern hung from a flagpole. However, just a few months later, in July, soldiers built and tended a shingled, 50-foot-tall wooden lighthouse with a copper-roofed iron lantern. It was the first light station established at a military installation in the British colonies.
The Ride of Paul Revere
On December 13, 1774, about four months before his more famous ride on the eve of the American Revolution, Paul Revere rode from Boston, Massachusetts, to warn the colonists of British plans to reinforce the fort and protect its gunpowder stores. However, about 400 men from Portsmouth, Rye, and New Castle raided the fort and removed 16 small cannons and 98 barrels of gunpowder. They also hauled down the fort’s huge British flag. Several injuries but no deaths occurred in the engagement. Many consider the attack to be the first overt act of the Revolution. They distributed arms and powder through several New Hampshire towns for potential use in the looming struggle against Great Britain.
British Governor John Wentworth immediately sent help to Boston, and the sloop Canceaux arrived on December 17, followed two days later by the frigate Scarborough. The latter had 40 guns and carried 100 British marines. This armed force prevented further raids by the Patriots, but it also produced a dangerous state of tension.
By the summer of 1775, Governor Wentworth, with his wife and infant son, took refuge in the fort and lived there for two months in the hope that a conflict could be avoided. British Admiral Samuel Graves soon sent a transport to dismantle the fort and remove the guns to Boston. On August 24, 1775, the governor and his family also sailed to Boston. Britain then abandoned the colony of New Hampshire to focus on the military situation in Massachusetts and relinquished control of the fort.
Portsmouth Harbor, New Castle, New Hampshire by Carol Highsmith.
As Portsmouth Harbor’s importance grew during the Revolutionary War, the shipbuilding industry expanded, and the Portsmouth Naval Shipyard was established in 1800. A new 85-foot-high wooden lighthouse was constructed in 1803 about 100 yards East of the original 1771 lighthouse. Additional fortification was also needed; improvements were made to the old fort, and it was renamed Fort Constitution in 1808. Renovations included a wall twice as high as the colonial fort’s, and new brick buildings were constructed. The fort was then garrisoned with a company of United States artillery. It was described in 1811 as “an enclosed irregular work of masonry, mounting 36 heavy guns… (with) brick barracks for two companies…”
During the War of 1812, the fort was manned and expanded, including the addition of Walbach Tower, equipped with a single 32-pounder cannon, which was constructed in 1814.
Portsmouth Harbor Light, 1860.
The fort remained serviceable during the Civil War, when various units were trained there. However, it needed to be replaced, and construction of a new fort, which was to be a massive, three-tiered granite structure, began, but it was never completed. Construction was abandoned in 1867.
In 1877, they demolished the old wooden lighthouse and replaced it with the current 48-foot-high cast-iron structure.
In 1897, construction began on Battery Farnsworth, located under the hill on which Walbach Tower stands. The battery was completed in 1899 and included two 8-inch guns. After the Spanish-American War of 1898, improving defenses of key harbors became a national priority. Built in 1904, Battery Hackleman, with two 3-inch guns, was designed primarily to defend this minefield against minesweepers.
The fort was further rebuilt and expanded through 1899 and remained active until World War II. In 1940-1944, the Harbor Defenses of Portsmouth were garrisoned by the 22nd Coast Artillery Regiment. A mine observation station was built atop Battery Farnsworth.
By 1948, Battery Hackleman was disarmed, and the fort was turned over to the Coast Guard. Afterward, Battery Hackleman was demolished. The State of New Hampshire received Fort Constitution in 1961, and it was listed on the National Register of Historic Places on July 2, 1973.
A portion of the ruins at Fort Constitution in New Castle, New Hampshire, by Carol Highsmith.
Today, Fort Constitution occupies three acres and includes Portsmouth Harbor Light, built in 1878, which remains a valuable aid to navigation. The State Park is located adjacent to the U.S. Coast Guard Station at the mouth of the Piscataqua River. It is open to the public.
More Information:
Fort Constitution Historic Site
25 Wentworth Road
New Castle, New Hampshire 03854
603-271-3556
©Kathy Alexander/Legends of America, updated October 2026.
Fort Constitution, New Hampshire by Carol Highsmith.
Also See:
New Hampshire – The Granite State
Forts Across the United States
Forts & Presidios Photo Gallery
Sources:
Fort Constitution Historic Site
New Hampshire State Parks
North American Forts
Wikipedia