The Soucook River is a 29.2 miles (47 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 central 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...

 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...

, 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...

.

The Soucook River begins at the outlet of Rocky Pond on the border between the towns of Canterbury

Canterbury, New Hampshire

Canterbury is a town in Merrimack County, New Hampshire, United States. The population was 2,352 at the 2010 census. Canterbury is home to Ayers State Forest and Shaker State Forest. On the last Saturday in July, the town hosts the annual .- History :...

 and Loudon, New Hampshire

Loudon, New Hampshire

Loudon is a town in Merrimack County, New Hampshire, United States. The population was 5,317 at the 2010 census. Loudon is the home of New Hampshire Motor Speedway....

. The river flows south through gently rolling terrain, soon entering Loudon and passing near the New Hampshire International Speedway

New Hampshire International Speedway

New Hampshire Motor Speedway is a oval speedway located in Loudon, New Hampshire which has hosted NASCAR racing annually since the early 1990s, as well as an IndyCar weekend and the oldest motorcycle race in North America, the Loudon Classic...

. The river passes through the village proper of Loudon, crossing a small dam, and continues south along a rapidly developing suburban corridor on the outskirts of Concord

Concord, New Hampshire

The city of Concord is the capital of the state of New Hampshire in the United States. It is also the county seat of Merrimack County. As of the 2010 census, its population was 42,695....

. The river forms the boundary between Concord and Pembroke

Pembroke, New Hampshire

Pembroke is a town in Merrimack County, New Hampshire, United States. The population was 7,115 at the 2010 census. Pembroke includes part of the village of Suncook. The center of population of New Hampshire is located in Pembroke.- History :...

 and ends at the Merrimack River downstream from Garvins Falls.

There are extensive sand and gravel deposits filling the Soucook River valley, which has led to the creation of several large excavation operations close to the river. New Hampshire Route 106

New Hampshire Route 106

New Hampshire Route 106 is a long secondary north–south highway in Merrimack and Belknap counties in central New Hampshire...

parallels the river throughout its course, crossing the river four times.