Fort Knox Credit: Linda Coan O'Kresik / BDN

Hard Telling Not Knowing each week tries to answer your burning questions about why things are the way they are in Maine — specifically about Maine culture and history, both long ago and recent, large and small, important and silly. Send your questions to

This week’s question comes to us from a comment left on a Bangor Daily News Facebook post a while back. The commenter wondered why there’s a huge granite fort in Prospect of all places — an awfully big structure for a small town without any other military installations for many miles around.

Why was Fort Knox built along the Penobscot River?

Fort Knox stands like a sentry in the town of Prospect, near the mouth of the Penobscot River, overlooking Bucksport Harbor — a granite edifice built in an era long ago, when ocean and river-going vessels still drove the economy and railroads were still in their infancy.

Though today it’s a tourist destination that hosts events ranging from Civil War reenactments to Halloween fright nights to modern dance performances, Fort Knox originally was built in the 1840s and ’50s, to protect Maine’s coastal interior and booming lumber industry from attack.

Civil war reenactors perform during a demonstration at Fort Knox.
A Confederate solider loads his musket during a School of the Soldier at Fort Knox in Prospect in 2016. Credit: Ashley L. Conti / BDN

Fort Knox’s placement on the river certainly makes sense — it’s up on a promontory where the river narrows before it opens up into Penobscot Bay, making it a good spot to watch out for and defend against approaching vessels — but it’s hard to imagine any foreign aggressors sailing up the river to attack, say, Orrington or Winterport.

But in the 1840s that was a legitimate concern. There were several precipitating events that spurred the military to secure the entry to the Penobscot River by building a fort. The first was the ill-fated Penobscot Expedition, the 1779 Revolutionary War battle that saw American forces attempt to force the British from eastern Maine via an armada of warships. The Americans were soundly defeated, in what has been called the worst domestic naval defeat in American history until the attack on Pearl Harbor in 1941.

The second was the Battle of Hampden during the War of 1812, when in 1814 the British sailed up the Penobscot and defeated U.S. forces in Hampden, later looting and burning both Hampden and Bangor. In 1838 and 1839, the Aroostook War, a border skirmish between Aroostook County and then-British colony New Brunswick, further drummed up anti-British sentiment and concerns about Maine’s vulnerability to attack — and given the lucrative Maine lumber industry, there was certainly a reason to worry about protecting such a valuable natural resource.

After the War of 1812, the government began to undertake an ambitious effort dubbed the “Third System,” to build a seacoast defense system along the eastern seaboard and the Gulf of Mexico. These forts would replace the deteriorating, often poorly-constructed ones built in the years after the U.S gained independence in 1783. Five forts were slated to be built in Maine, including Fort Knox, Fort Popham in Phippsburg, Fort Gorges and Fort Scammell in Portland and Fort Preble in South Portland.

Between 1821 and 1869, the U.S government built 47 forts nationwide, though not all — including Fort Preble — were actually fully finished. Work on Fort Knox began in 1844, with the fortress to be constructed out of granite quarried at nearby Mt. Waldo in Frankfort. It was named for Gen. Henry Knox, a Thomaston resident and the first U.S. secretary of war. Fort Knox’s roof, in fact, was never fully completed by the time funding for the project was cut in 1869, according to Maine’s Bureau of Parks and Lands.

A cannon inside of Fort Knox.
An interior view of Fort Knox in Prospect, showing one of the historic cannons, which if it had ever been used during wartime would have fired on enemy ships through an opening in the granite wall. Credit: Linda Coan O’Kresik / BDN

Despite it taking 25 years to build and costing the equivalent of approximately $38 million, adjusted for inflation, Fort Knox never saw a single battle, and hasn’t been manned since the turn of the 20th century. There was a Civil War regiment stationed there, though they mostly did training exercises, and a Connecticut regiment was stationed there during the Spanish American War. That’s it.

The federal government sold Fort Knox to the state of Maine in 1923, and since 1943 it’s been a state historic site. It’s now managed by local nonprofit the Friends of Fort Knox. Today, it’s one of the best-preserved forts of its kind in the country. In 2007, the Penobscot Narrows Bridge and its observation tower opened adjacent to the fort, adding another major landmark to the historic site — a structure built for war but which has only seen peace during its 178 years of existence.

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Emily Burnham

Emily Burnham is a Maine native and proud Bangorian, covering business, the arts, restaurants and the culture and history of the Bangor region.