was intermittent, and the fort's design was never fully completed despite an expenditure of $1,000,000. Granite was quarried five miles (8 km) upriver from Mount Waldo in Frankfort. The fort's overall design was by Joseph G. Totten, the foremost fortification engineer of the Army Corps of Engineers in his day. Notable engineer officers supervising construction included Isaac Ingalls Stevens and Thomas L. Casey. Besides the main fort with 64 guns, Fort Knox had two open water batteries facing the river, each equipped with a shot furnace to heat cannonballs sufficiently that they could ignite wooden ships if the ball lodged in the vessel. These furnaces became obsolete with the adoption of ironclad warships. Civil War Fort Knox never saw battle, though it was manned during times of war. During the American Civil War volunteers from Maine, mostly recruits in training before assignment to active duty, manned the fort. Thomas Lincoln Casey supervised work on the fort, including adapting the batteries to use the recently invented Rodman cannon, and oversaw its completion. Spanish–American War A regiment from Connecticut manned Fort Knox during the Spanish–American War. A plaque at the fort describes the laying of a controlled minefield in the river during this war, which Congress appropriated $3,200 for shortly after its outbreak. Post Spanish–American War The garrison was reduced to one man, the "Keeper of the Fort" or caretaker with the rank of ordnance sergeant, at the end of the war. The keeper attended to the condition and maintenance of the fort, and reported to Fort Preble in South Portland. In 1900 the fort received a permanent "torpedo storehouse" for storing naval mines (which were called torpedoes at the time) that is now the Visitor's Center. In 1923, the federal government declared the fort excess property and put its grounds up for sale. The state of Maine bought it for $2,121. It has been administered as a Maine state historic site since 1943. A work crew from the Ellsworth camp of the Civilian Conservation Corps, Co. 193 was deployed to transform the fort into a tourist destination. The November 1936 issue of Brann News, the camp newspaper lists work accomplished: "picnic area, reforestation, road construction, drainage in fort itself, Spring development, table and bench combinations, fireplaces, reconstruction of the retaining wall on the river side of the fort, repairing masonry work, in the interior of the fort." Present The fort today