Not to be confused with the one in Kentucky with all the gold, the building of the massive granite Fort Knox (Rte. 1, 207/469-6553, http://fortknox.maineguide.com, May–Oct., $3 adults, $1 children 5–11, free children under 5) began in 1844 and continued over the next 25 years. These days, it’s difficult to conceive of anyone invading eastern Maine, but the British had done so twice, in 1779 and 1814, even briefly annexing the region on the latter occasion, and so the early Americans were determined that it not happen again.

A model of strategic design, the fort is a delight to explore, either in the company of a state park tour guide or alone with a flashlight. Long, dark passageways lead down to cannons pitched over the river, and corridors flanking the entrance are rife with murder holes to pick off invading troops. Alas, before Fort Knox was even completed, it was rendered obsolete by modern advances in warfare.

Complementing the fort is the adjoining Penobscot Narrows Bridge and Observatory (9 a.m.–5 p.m. daily, open until 6 p.m. Jul.–Aug.), which incorporates a public viewing deck a dizzying 437 feet above Penobscot Bay. Needless to say, the views 15 miles in every direction are breathtaking, making the bridge an instant tourist attraction onto which Bucksport has latched for its future revitalization.

Entrances to the observatory are through Fort Knox; tickets are time-stamped, and the price includes entrance into the fort, so you can explore the historic site while you wait for your trip up the elevator.