Great Stone Dam Lawrence

The Great Stone Dam was built between 1845 and 1848 on the site of Bodwell's Falls on the Merrimack River in what became Lawrence, Massachusetts. The dam has a length of 900 feet and a height of 35 feet.Lawrence is in Essex County, Massachusetts, approximately 25 miles north of Boston and only a few miles south of the New Hampshire border, located in the Merrimack Valley. The dam is 11 miles downstream from Lowell and is visible from Route 28 in Lawrence and from behind the Pacific Paper Mill.The dam feeds two canals.

Source: Wikipedia