Description - The first military installation on this site was an earthwork fort (redoubt) with four "great guns" erected in 1632. The fort was named Fort William and Mary. It was followed by a timber blockhouse built in 1666. In 1791 the state of New Hampshire gave the United States the neck of land on which Fort William and Mary and a lighthouse were situated. The fort was repaired, renamed Fort Constitution and garrisoned with a company of United States artillery.
- In 1791 the state of New Hampshire gave the United States the neck of land on which Fort William and Mary and a lighthouse were situated. The fort was repaired, renamed Fort Constitution and garrisoned with a company of United States artillery. Renovations which included a wall twice as high as that of the colonial fort and new brick buildings were completed in 1808. It is the ruins of this fort that are seen today. The fort was used during the War of 1812 and was still serviceable during the Civil War when various units were trained there.
Improvements in artillery during the nineteenth century made it clear the old fort would have to be replaced. A new one was begun during the Civil War. It was to be a massive, three-tiered granite structure, but like others begun at the same time, was never completed. Armored steam powered warships with heavy guns made the masonry fort obsolete.
Outside the old fort in the area now occupied by the coast guard, a completely new system of fortifications was built between 1897 and 1903. This included a battery of two eight-inch guns on disappearing carriages, a mines casement, cable tank and a storage house for mines. The harbor was protected by mines during the Spanish American War and during World War I and II. Fort Constitution was returned to the state in 1961 and place on the National Register of Historic Places on July 2, 1973.
Recreation - The 2-acre historic site, located along the Atlantic Ocean, offers a self-guided walking tour for which no fee is collected.
Climate - Winter can be cold with average temperatures ranging around 19 degrees Fahrenheit. The cold temperatures humidity bring heavy, water-laden snow to all parts of the state. Spring begins in mid-March and lasts through May. This time of the year is referred to as mud season in the mountains. The sugar is flowing early in the season and wild flowers bloom toward the end of it. Summer is the busiest season of the year for the tourism industry. This is an excellent time to travel, mountain roads are open and most of the mud has dried. Average summer temperatures range around 68 degrees Fahrenheit. Fall brings the leaf lookers to see the spectacular colors of the deciduous trees. Expect to see bus loads of people enjoying the crisp fall New England weather.
The fort is located on SR 1B at U.S. Coast Guard Station, New Castle.