Named after Major General Henry Knox, America's first Secretary of War and Commander of Artillery in the American Revolution, Fort Knox stands guard over the Penobscot River and the surrounding area. Because the area has been the scene of several different conflicts, the decision was made to construct Fort Knox along the Penobscot River.

The granite that forms the structure of Fort Knox was quarried at Mount Waldo, which is approximately five miles up the Penobscot River. The large blocks of granite were cut, taken down the mountain, and then transported by barges on the river to the wharf at Fort Knox.

The fort saw two periods of military activity, during the Civil War and again during the Spanish-American War. At an expense of nearly a million dollars, Fort Knox took over 25 years to be completely constructed.