Nashua River - Definition and Overview

The Nashua River is a tributary of the Merrimack River in Massachusetts and New Hampshire in the United States. It rises west of Boston and flows generally north past Groton, joining the Merrimack at Nashua, New Hampshire.

The river was heavily used for industry during the colonial period and the early United States. During the late 18th century and early 19th century, the heavy concentration of dye manufacturing near Groton resulted in pollution that notoriously turned the river various colors downstream from the factories. With the near total decline of industry in the region, the river has largely recovered.