Built in the mid 1800s, Fort Knox, now more popularly known as Fort Knox State Historic Site or Fort Knox State Park is the very first fort in the state that is built of granite. It was built in consequence of the Aroostook War when the US and the UK where having issues about the Canadian border.

Fort Knox? batteries faced the water to aptly protect Bangor, Maine and the Penobscot River. Bangor was a primary producer of shipbuilding lumber, so it was necessary to defend it in case a war breaks out.

Fort Knox got its name from the first US Secretary of War, Henry Knox. It was declared a Maine state historic site and a National Historic Landmark in 1970.