War and the 1842 Webster-Ashburton Treaty. The blockhouse was built in 1844 near the former upper battery; this was the last blockhouse built at a fort in Maine, and probably one of the last in a US coastal fort. The fort saw active use during the American Civil War, at which time it achieved much of its present structure due to a rebuilding under the third system that was never completed. The fort was manned near the start of the war by the Maine Coast Guard and the Kittery Artillery company, and in 1864 was also manned by the Maine State Guard. Its Civil War garrison notably included Vice President Hannibal Hamlin, who enlisted in Company A of the Maine State Guard as a private and served as a cook in the fort. Some subsequent citations erroneously confuse his unit with the Maine Coast Guard — including a plaque at the fort. The fort saw little action during the Civil War. A major rebuilding and expansion began in 1863 as part of the third system of fortifications, and the intent was to create a large five-sided fort with one or two tiers of cannon all around. However, only the seawalls were completed on the two seaward fronts, along with one of the landward cannon bastions with a granite magazine. The seawall was defended by a small caponier with rifle ports. Based on war experience, masonry forts were assessed as vulnerable to rifled cannon, and funding was withdrawn from all masonry fort projects in 1867, leaving Fort McClary with few cannon positions. A large number of granite blocks remain at the fort to this day. Post Civil War to present In the 1870s, the lower battery was rebuilt with three temporary gun positions for 10-inch Parrott rifles, but funding was again cut off with few other improvements. In the 1890s, nine 15-inch Rodman smoothbore guns and seven carriages were stored at the fort, to be mounted in case of war. Three of the Rodmans were mounted as an emergency measure in the Spanish–American War of 1898. The fort was superseded by the construction of Fort Foster (Kittery, Maine) and new batteries at Fort Constitution under the Endicott Program by 1901. By the 1910s, most of the fort had fallen into disrepair and it was officially decommissioned in 1918. The State of Maine acquired most of the property from the federal government