Concord River

The Concord River is a 16.3-mile-long tributary of the Merrimack River in eastern Massachusetts in the United States. The river drains a small rural and suburban region northwest of Boston. One of the most famous small rivers in U.S. history, it was the scene of an important early battle of the American Revolutionary War and was the subject of a famous 19th-century book by Henry David Thoreau.

The river begins in Middlesex County, formed by the confluence of the Sudbury and Assabet rivers at Egg Rock, near the Concord town center. It flows generally north, from eastern Concord , joining the Merrimack River from the south on the eastern side of Lowell. It is a gently flowing stream with little variation in topography along most of its route. Its drainage basin stretches into Worcester County and includes 36 towns within Massachusetts.

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