Antique Real Photo Postcard. A ship passes by Fort Knox in Prospect, Maine in Penobscot Narrows. Caption is light but reads, Fort Knox, Prospect, ME." Card No. 8010. Published by Eastern Illustrating Co. Divided back, postmarked 1937 from Stockton Springs, Maine. Condition: Card has long crimp in upper portion of sky. Comments: Fort Knox, now Fort Knox State Park or Fort Knox State Historic Site, is located on the western bank of the Penobscot River in the town of Prospect, Maine, about 5 miles from the mouth of the river. Built between 1844 and 1869, it was the first fort in Maine built entirely of granite; most previous forts used wood, earth, and stone. It is named after Major General Henry Knox, the first U.S. Secretary of War and Commander of Artillery during the American Revolutionary War, who at the end of his life lived not far away in Thomaston. The fort was designated a National Historic Landmark in 1970, as a virtually intact example of a mid-19th century granite coastal fortification. Fort Knox also serves as the entry site for the observation tower of the Penobscot Narrows Bridge that opened to the public on 19 May 2007.