Merrimack River

Merrimack River
Merrimac River
The Merrimack River in Lowell, Massachusetts
Country	United States
State	New Hampshire  Massachusetts
Region	New England
Tributaries
- right	Contoocook River, Piscataquog River, Souhegan River, Nashua River, Concord River
Cities	Concord, New Hampshire, Manchester, New Hampshire, Nashua, New Hampshire, Lowell, Massachusetts, Lawrence, Massachusetts, Haverhill, Massachusetts, Newburyport, Massachusetts
Source	Pemigewasset River-Winnipesaukee River juncture
- location	Franklin, Merrimack County, New Hampshire, United States
- elevation	280 ft (85 m)
- coordinates	43°26′11″N 71°38′53″W / 43.43639°N 71.64806°W / 43.43639; -71.64806
Mouth	Atlantic Ocean
- location	Newburyport, Essex County, Massachusetts, United States
- elevation	0 ft (0 m)
- coordinates	42°49′10″N 70°48′43″W / 42.81944°N 70.81194°W / 42.81944; -70.81194Coordinates: 42°49′10″N 70°48′43″W / 42.81944°N 70.81194°W / 42.81944; -70.81194
Length	117 mi (188 km)
Basin	4,635 sq mi (12,005 km2)
Discharge	for Newburyport, Massachusetts
- average	7,562 cu ft/s (214 m3/s)
The Merrimack River and its major tributaries

The Merrimack River (or Merrimac River, an occasional earlier spelling) is a 117-mile-long (188 km) river in the northeastern United States. It rises at the confluence of the Pemigewasset and Winnipesaukee rivers in Franklin, New Hampshire, flows southward into Massachusetts, and then flows northeast until it empties into the Atlantic Ocean at Newburyport. From Pawtucket Falls in Lowell, Massachusetts, onward, the Massachusetts–New Hampshire border is roughly calculated as the line three miles north of the river.

The Merrimack is an important regional focus in both New Hampshire and Massachusetts. The central-southern part of New Hampshire and most of northeast Massachusetts is known as the Merrimack Valley.

Several U.S. naval ships have been named the USS Merrimack and USS Merrimac in honor of this river.

Prior to glaciation, the Merrimack continued its southward course far beyond the present day New Hampshire-Massachusetts border to enter the Atlantic Ocean near Boston. Upon the glacier's retreat, debris deposited north of Boston filled the lower Merrimack Valley, redirecting the river into its current northeast bend at Lowell. The Neville archaeological site is located along the river's banks in New Hampshire.

The total watershed of the river is approximately 4,700 square miles (12,200 km²), covering much of southern New Hampshire and a portion of northeastern Massachusetts. On its banks are a number of cities built to take advantage of water power in the 19th century, when textile mills dominated the New England economy: Concord, Manchester, and Nashua in New Hampshire, and Lowell, Lawrence, and Haverhill in Massachusetts. At the mouth of the river is the small city of Newburyport. Prior to the construction of the Middlesex Canal, Newburyport was an important shipbuilding city, in a location to receive New Hampshire timber that had been floated downriver. The river enters Massachusetts at the town of Tyngsborough and from there, winds past or through Chelmsford, Lowell, Dracut, Tewksbury, Andover, Methuen, Lawrence, North Andover, Haverhill, Groveland, West Newbury, Merrimac, Amesbury, Newburyport, and Salisbury.