The Nissitissit River is a 10.5 miles (16.9 km) river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 located in southern New Hampshire

New Hampshire

New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

 and northern Massachusetts

Massachusetts

The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Nashua River

Nashua River

The Nashua River, long, is a tributary of the Merrimack River in Massachusetts and New Hampshire in the United States. It is formed in eastern Worcester County, Massachusetts, by junction of its north and south branches near Lancaster, and flows generally north-northeast past Groton to join the...

, itself a tributary of the Merrimack River

Merrimack River

The Merrimack River is a 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...

, which flows to the Gulf of Maine

Gulf of Maine

The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America.It is delineated by Cape Cod at the eastern tip of Massachusetts in the southwest and Cape Sable at the southern tip of Nova Scotia in the northeast. It includes the entire coastlines of the U.S...

. This river is part of the Nashua River Watershed

Nashua River Watershed

The Nashua River Watershed is a major Massachusetts watershed.-Description:From its impoundment at the Wachusett Reservoir in Clinton, Massachusetts, the South Branch of the Nashua River flows north and joins the North Branch of the Nashua River in Lancaster, Massachusetts. The North Branch of the...

.

The Nissitissit River begins at the outlet of Potanipo Pond in the town of Brookline, New Hampshire

Brookline, New Hampshire

Brookline is a town in Hillsborough County, New Hampshire, United States. The population was 4,991 at the 2010 census. Brookline is home to the Talbot-Taylor Wildlife Sanctuary.-History:...

. It flows southeast at a very mild gradient, crossing the southwest corner of Hollis, New Hampshire

Hollis, New Hampshire

Hollis is a town in Hillsborough County, New Hampshire, United States. The population was 7,684 at the 2010 census. The town center village is listed on the National Register of Historic Places as Hollis Village Historic District....

 before entering Massachusetts, where it joins the Nashua River in the town of Pepperell

Pepperell, Massachusetts

Pepperell is a town in Middlesex County, Massachusetts, United States. The population was 11,497 at the 2010 census. It includes the village of East Pepperell.-History:...

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