The Concord River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data
The National Map
, accessed October 3, 2011 tributary of the Merrimack River in eastern Massachusetts in the United States. The river drains a small rural and suburban region northwest of

Boston Boston (), officially the City of Boston, is the capital city, state capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts, as well as the cultural and financ ...

. 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 The American Revolutionary War (April 19, 1775 – September 3, 1783), also known as the Revolutionary War or American War of Independence, was a major war of the American Revolution. Widely considered as the war that secured the independence of ...

and was the subject of a famous 19th-century book by

Henry David Thoreau Henry David Thoreau (July 12, 1817May 6, 1862) was an American naturalist, essayist, poet, and philosopher. A leading Transcendentalism, transcendentalist, he is best known for his book ''Walden'', a reflection upon simple living in natural su ...

Description and early history

The river begins in Middlesex County, formed by the confluence of the

Sudbury Sudbury may refer to: Places Australia * Sudbury Reef, Queensland Canada * Greater Sudbury, Ontario (official name; the city continues to be known simply as Sudbury for most purposes) ** Sudbury (electoral district), one of the city's federal e ...

and Assabet rivers at Egg Rock, near the Concord town center. It flows generally north, from eastern Concord (along the northwestern edge of the Boston metropolitan area), 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. Native Americans called it the ''Musketaquid'' or "grass-grown" river because of its sluggish waters abound in aquatic or semi-aquatic vegetation and its banks are fringed with wild grasses and sedges which stretch for miles along both sides of this placid stream. This creates a good environment for a variety of fish, including

bass Bass or Basses may refer to: Fish * Bass (fish), various saltwater and freshwater species Music * Bass (sound), describing low-frequency sound or one of several instruments in the bass range: ** Bass (instrument), including: ** Acoustic bass gui ...

shad The Alosinae, or the shads,Alosinae

, and alewife (river herring), pickerel,

carp Carp are various species of oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in parts of ...

, and

American eel The American eel (''Anguilla rostrata'') is a facultative catadromous fish found on the eastern coast of North America. Freshwater eels are fish belonging to the elopomorph superorder, a group of phylogenetically ancient teleosts. The America ...

. Native Americans wove sticks in intricate designs to trap Alewives and other migrating fish at the mouths of rivers throughout this region. By 1635, settlers from England began to arrive, and they gave the river its present name. On April 19, 1775, the Old North Bridge over the river in the town of Concord was famously the scene of the

Battle of Concord The Battles of Lexington and Concord were the first military engagements of the American Revolutionary War. The battles were fought on April 19, 1775, in Middlesex County, Province of Massachusetts Bay, within the towns of Lexington, Concord ...

(on the same day when the first shots of the Revolutionary War were fired at nearby Lexington). The current version of the bridge (a reproduction) is preserved by the National Park Service.

wrote his first book, '' A Week on the Concord and Merrimack Rivers'', in 1849 while living at nearby Walden Pond. His book recounted a seven-day boat trip on the rivers with his brother John, who had since died. Thoreau recounted his exploration of the natural beauty of the river, and his accompanying thoughts on such eternal themes as truth, poetry, travel, and friendship. Despite the growth of the suburbs in the vicinity of the river, it remains a popular canoeing destination today. The last mile of the river in Lowell is serious class 3+/4 whitewater.

Dams cause fish population to decrease

Dams were built along the Concord River to increase crop production and also to provide a source of power for operating mills. By the 19th century, the native population of shad and alewife became extinct, because the dams prevented the mature fish from returning upstream to spawn. Alewife and other anadromous fish are migratory. They hatch in freshwater, make their way to the sea to grow, then return as adults to freshwater to spawn, usually near where they had hatched. This instinct is imprinted within the fish when it is born. So, when the route upstream became blocked, the cycle was broken. The Faulkner Dam in

North Billerica North Billerica is an unincorporated village of the town of Billerica, Massachusetts, United States, one of the nine sections (hamlets) that make up the Town of Billerica. It is the home to Faulkner and Talbot mills and the North Billerica Trai ...

is just one of many blockages that caused the alewife population to collapse on the Concord River. At this point, water was diverted north to Lowell and south to Charlestown to run the Middlesex Canal.

Effects of pollution

During the 19th century, the Concord River was near the heart of the US Industrial Revolution. Textile, paper,

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, and mining industries all emerged during this period. Industrial wastes were dumped into the river, along with untreated

sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residenc ...

and other organic waste. Industrial development within the watershed peaked in the 1920s. The early 1960s saw an increase in the number of chemical and metal firms, many supporting the

electronics industry The electronics industry is the economic sector that produces electronic devices. It emerged in the 20th century and is today one of the largest global industries. Contemporary society uses a vast array of electronic devices built-in automated or ...

within the

metropolitan area. By the 1960s, the Merrimack River was considered one of the top ten most polluted waterways in America. The Concord River empties into the Merrimack River. The passage of the

Clean Water Act The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the responsibiliti ...

in 1972 signaled the beginning of US efforts to improve the quality of its waterways. The act imposed stricter controls on point source discharges into rivers and other navigable waters. This eventually led to the installation of three wastewater treatment plants on the banks of the Concord River: one in Concord and two in Billerica. These plants have helped to prevent subsequent damage to the river ecosystem when they were able to operate within federally mandated limits. Pollutants such as

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and PCBs remain trapped in the sediment. Throughout much of the Sudbury River and downstream into the Concord River, fish consumption is banned due to

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

-laden sediments from the Nyanza

Superfund Superfund is a United States federal environmental remediation program established by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The program is administered by the United States Environmental Pro ...

site and other sources. Perchlorate was detected in the Concord River in August 2004. Initially, it was believed that

explosives An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...

used in road and building construction were the source of this pollutant. However, an investigation by the town of Billerica eventually determined that the source was a local company that produced surgical and medical materials. The company was using 220 gallons per month of perchloric acid in a bleaching process, and rinse water was being discharged into the sewage system. After the company was identified, it voluntarily shut down until ion exchange equipment could be installed in accordance with environmental guidelines. In May 2007, Billerica was the subject of legal action and forced to pay a $250,000 penalty for discharging pollutants into the Concord River. The action was brought by the U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (MassDEP) because the town of Billerica exceeded allowable effluent limits for phosphorus, fecal coliform bacteria, pH, and ammonia nitrogen. The town was also charged with failing to submit discharge monitoring reports, failing to comply with monitoring requirements, and failing to submit infiltration and inflow reporting. According to the EPA, Billerica's discharges of phosphorus created an overabundance of nutrients, which damaged the river by stimulating excessive

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They