Fort Constitution State Historic Site The original military outpost was built here in 1632 and rebuilt in 1666. One of the first actions of the American revolution was when group of patriots in 1774 raided the fort which was then called Fort William and Mary and captured a cache of weapons that were later used during the Battle of Bunker Hill. The fort was renamed Fort Constitution in 1791 and renovated in 1808 which is when the ruins you can see today date from.
The ruins of the fort and grounds are unstaffed but is open year round for picnics and recreation.
The Portsmouth Harbor Lighthouse is also on site but not open to the public except during open houses during the summer. The best views of the lighthouse are from the harbor but you can get some shots from the fort.
We love going to sites like this where you can get little nuggets of history you would have been totally unaware of before visiting.