Beaver Brook is a 30.7 miles (49.4 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 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 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 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...

, part of 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...

 watershed

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

.

Beaver Brook rises in Chester, New Hampshire

Chester, New Hampshire

Chester is a town in Rockingham County, New Hampshire, United States. The population was 4,768 at the 2010 census. It is home to Chester College .-History:Incorporated in 1722, Chester once included Candia, set off in 1763...

, and flows south into Derry

Derry, New Hampshire

-Climate:-Demographics:As of the census of 2010, there were 33,109 people, 12,537 households, and 8,767 families residing in the town. The population density was 924.8 people per square mile . There were 13,277 housing units at an average density of 143.2/km²...

, passing through Harantis Lake, Adams Pond, and Beaver Lake. Continuing south, the brook forms the boundary between Londonderry

Londonderry, New Hampshire

-Demographics:As of the census of 2000, there were 23,236 people, 7,623 households, and 6,319 families residing in the town. The population density was 555.8 people per square mile . There were 7,718 housing units at an average density of 184.6 per square mile...

 and Windham

Windham, New Hampshire

Windham is a town in Rockingham County, New Hampshire, United States. The population was 13,592 at the 2010 census.- History :The area was initially home to the Pawtucket Native Americans. Scottish immigrants began to settle in the area in 1719. The region was known as “Nutfield” and included what...

, then flows through Pelham

Pelham, New Hampshire

The earliest census data shows the town of Pelham having a population of 543 residents in 1767.As of the census of 2000, there were 10,914 people, 3,606 households, and 2,982 families residing in the town. The population density was 412.9 people per square mile . There were 3,740 housing units at...

. The brook crosses the state line into Dracut, Massachusetts

Dracut, Massachusetts

Dracut is a town in Middlesex County, Massachusetts, United States. As of the 2010 census, the town population was 29,457. Dracut is primarily a suburban community, belonging to Greater Lowell and bordering southern New Hampshire...

, and reaches 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...

 in the city of Lowell

Lowell, Massachusetts

Lowell is a city in Middlesex County, Massachusetts, USA. According to the 2010 census, the city's population was 106,519. It is the fourth largest city in the state. Lowell and Cambridge are the county seats of Middlesex County...

.

Most of the brook's course is through gently hilly terrain that is rapidly being converted into suburb

Suburb

The word suburb mostly refers to a residential area, either existing as part of a city or as a separate residential community within commuting distance of a city . Some suburbs have a degree of administrative autonomy, and most have lower population density than inner city neighborhoods...

an land use.