The Merrimack Valley is a bi-state region along the Merrimack River in the U.S. states of New Hampshire and Massachusetts, United States. The Merrimack is one of the larger waterways in the New England region and has helped define the livelihood and culture of those living along it since native times.Major cities in the Merrimack Valley include Concord, Manchester and Nashua in New Hampshire, as well as Lowell, Lawrence, Haverhill and Newburyport in Massachusetts.