The South Branch of the Piscataquog River is a 20.5 miles (33 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...

 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 Piscataquog River

Piscataquog River

The Piscataquog River is a river located in southern New Hampshire in the United States. It is a tributary of the Merrimack River, which flows to the Gulf of Maine....

, part 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...

 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...

.

The South Branch of the Piscataquog begins at the outlet of Pleasant Pond in Francestown, New Hampshire

Francestown, New Hampshire

Francestown is a town in Hillsborough County, New Hampshire, United States. The population was 1,562 at the 2010 census.- History :Incorporated in 1772, Francestown takes its name from Frances Deering Wentworth, the wife of colonial governor John Wentworth. There were 928 residents when the first...

. The river travels south-southeast until entering New Boston

New Boston, New Hampshire

New Boston is a town in Hillsborough County, New Hampshire, United States. The population was 5,321 at the 2010 census. New Boston is home to the annual Hillsborough County Agricultural Fair and the Molly Stark Cannon.-History:...

, where it turns northeast to flow to the Piscataquog River just over the town line in Goffstown

Goffstown, New Hampshire

Goffstown is a town in Hillsborough County, New Hampshire, United States. The population was 17,651 at the 2010 census. The compact center of town, where 3,196 people resided at the 2010 census, is defined by the U.S. Census Bureau as the Goffstown census-designated place and is located at the...

. For most of its route, the South Branch passes through rolling, hilly country, occasionally dropping over small waterfalls. New Hampshire Route 13

New Hampshire Route 13

New Hampshire Route 13 is a long north–south state highway in the state of New Hampshire, United States. The highway runs from Brookline to Concord....

follows the river closely from New Boston to Goffstown.