Old Furnace State Park in Killingly preserves the landscape of an early ironworks that operated from before the American Revolutionary War into the mid-nineteenth century. During the Revolution, iron produced here was made into horseshoes sold to the Continental Army, and later the furnace supplied metal parts for nearby cotton mills. The site used local bog ore, charcoal, limestone, gabbro, and waterpower along a fall line, and by the eighteen thirties it also included a gristmill before local resources were exhausted. Acquired by the town in 1909 and transferred to the state in 1918, the park later expanded substantially and still contains surviving industrial traces amid forest, wetlands, ponds, and trails.