Big Otter is a rare example of a mill with a bellcast mansard roof and pedimented dormers. A mill existed at this site in the late eighteenth century, but after its nineteenth-century replacement was washed away in a flood in 1917, its then owner, Reed Forbes, built this one. The frame, two-and-a-half-story mill on a raised basement has a metal waterwheel, four roller mills, and one stone mill. Its small, one-story wing served as an office and workshop for the miller until the operation closed in the 1940s. In almost all of its four stories, the equipment is intact.