Fort William and Mary

Fort William and Mary is a stone fortification at the mouth of the Piscataqua River that defended Portsmouth Harbor. The installation has thick walls, several gun emplacements, and spreads across the rocky island where it was built.

The fort was built during colonial times and played an important role in defending the northern harbor. In December 1774, Patriots raided the installation to secure gunpowder and cannons before the American Revolution began.

The fort shows how colonists protected their coastline and what building methods they needed for defense. You can see in the walls and gun positions how closely military strategy and harbor protection were connected.

The site is freely accessible from dawn to dusk and sits on an island easily reached on foot from New Castle. The best time to visit is during clear weather, when views of the harbor and surrounding area are most rewarding.

The fort was the first place where British troops were stationed in New Hampshire and housed the largest ammunition storage in the northern region. This strategic importance made it a target for early patriotic action before the conflict erupted.

Location: New Castle

GPS coordinates: 43.07132,-70.71021

Latest update: December 7, 2025 20:23