Merrimack River

• 1. Introduction

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  The Merrimack River carries two contradictory reputations. In the 1960s it ranked among the ten most polluted waterways in the entire United States. Yet Henry David Thoreau made it the subject of one of early American literature's most celebrated journeys. The river begins at the confluence of two other rivers in Franklin, New Hampshire, runs 117 miles south and then northeast, and finally empties into the Gulf of Maine at Newburyport. Along the way it passes cities that once ran on its power and towns that dumped into its waters for generations. How a river becomes this central to a region's identity, its economy, its literature, and its environmental crises is a story that starts long before European settlers ever arrived.

• 2. A Name in Dispute

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  In 1604, French colonists bound for Acadia heard native people describe a beautiful river to the south. The French wrote down what they heard as "Merremack," and the following year Samuel de Champlain located the river and promptly renamed it Riviere du Gas. The French name did not stick, but the native name did, in slightly altered form.

  What the name actually means has never been settled. Joseph B. Walker, drawing on Chandler Eastman Potter's The History of Manchester from 1856, argued that the elements merruh and auke combine to mean "the place of strong current," a reading Potter called fitting given the river's rapids. Thoreau, in A Week on the Concord and Merrimack Rivers, offered a different reading entirely, implying the name signifies "the Sturgeon River." Both interpretations carry some weight, since the river has both strong currents and, historically, sturgeon.

  The spelling wars ran for centuries. William Wood's New England's Prospect of 1634 called it the "Merrimacke" and placed it eight miles beyond Agowamme, the settlement now known as Ipswich, Massachusetts. A 1721 land grant at Penacook, New Hampshire, used "Merrimake" and "Merrymake." Merrimack, New Hampshire, incorporated in 1746, spelled its own name "Marrymac" in the record of its first town meeting and was still written as "Merrimac" in the 1810 census; only from the 1820 census onward did "Merrimack" become consistent. US Congressman John Jacob Rogers of Massachusetts petitioned Congress in 1914 to make "Merrimack" the official spelling, giving a centuries-long argument its formal resolution.

• 3. Ice, Industry, and Water Power

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  Around 14,000 years ago, a retreating glacier deposited debris north of Boston that filled the lower Merrimack Valley and bent the river's course sharply northeast at what is now Lowell. Before that, the river had continued south and entered the Gulf of Maine near Boston. That ancient redirection put Pawtucket Falls at Lowell in the path of the current, and the falls would eventually power a revolution in American manufacturing.

  By the 19th century, the Merrimack anchored an entire regional economy built on textile mills. Concord, Manchester, and Nashua in New Hampshire and Lowell, Lawrence, and Haverhill in Massachusetts all grew up on its banks precisely because the river's flow could be harnessed. Before the Middlesex Canal connected the waterway to wider trade routes, Newburyport at the river's mouth was already an important shipbuilding city, positioned to receive timber floated down from New Hampshire forests. The river's watershed covers 5,010 square miles, making it the fourth largest river basin in all of New England, and that scale gave the mills a reliable, high-volume water supply for decades.

  At Lowell, that industrial heritage produced one of the river's most durable structures. The Great Gate, also called the Francis Gate, was built in 1850 under the direction of James B. Francis to seal the city's canal system from the Merrimack when floods threatened. Critics considered it unnecessary when it was first built, and the project earned the nickname "Francis' Folly." Two years later, in 1852, the gate proved its worth during a major flood, and it saved the city again during the great flood of 1936.

• 4. Pollution and Its Reckoning

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  Since 1951, the river accumulated damage at a steady rate. Textile mills used it as a discharge channel for factory waste. Raw sewage, paper mill effluent, tannery sludge, and industrial chemicals all entered the water over decades of unregulated use. In 1966, environmentalist Donald Eaton Carr described the Merrimack as being "haunted with the oldest and most hopeless pollution of any in the country."

  Phthalates, chemicals used in plastic manufacturing and harmful to human health, were found in high concentrations in the river in 1973. A study the following year, in 1976, found that road salt had by then become the single largest source of pollution. By 2002, a statewide water assessment identified elevated E. coli and fecal coliform counts as the primary cause of water quality violations. Combined sewer overflow, in which untreated sewage flows directly into the river when infrastructure is overwhelmed, became the dominant concern in the 2000s. Six sanitary sewer systems currently discharge untreated sewage directly into the Merrimack as a result of infrastructure failures.

  The Federal Clean Water Act of 1972 changed the trajectory. It required sewage treatment before discharge into waterways, and federal funding built new wastewater infrastructure along the river. Citizens began reporting the return of American shad, striped bass, trout, and Atlantic salmon. The improvement was real, but a 1997 study found that the long-term effects of pollution persisted: elevated bacteria counts, low dissolved oxygen, and high nutrient levels remained. Recent research has identified mercury contamination as a growing threat to fish and aquatic life, with biological hotspots and watershed-level mercury transport compounding the risk.

• 5. Floods That Shaped the Valley

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  March 1936 brought the worst flood in the Merrimack's recorded history. Rain and melting snow combined to raise the river at Lowell to 68.4 feet, ten feet higher than any flood since. Jack Kerouac set part of his novel Doctor Sax during that event, preserving the catastrophe in American fiction. The Francis Gate, which had been dropped in 1936, was left in place afterward, and that decision prevented flooding when the New England Hurricane of 1938 struck the region.

  On the 15th of May, 2006, a different kind of flood arrived. Rainfall raised the Merrimack more than eight feet above flood stage at Lowell. Most areas received roughly a foot of rain; some received as much as 17 inches. Around 1,500 people were evacuated from their homes, according to reporting by The Boston Globe. In Haverhill, Massachusetts, the flood broke the main sewage pipeline, dumping raw sewage waste into the river. The city of Lowell responded by installing a modern, though temporary, flood control gate made of square steel beams at the site of the historic Francis Gate. Floods in October 1996 and April 2007 round out the list of the river's most serious recorded events at Lowell.

• 6. The River in American Culture

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  Henry David Thoreau's A Week on the Concord and Merrimack Rivers stands as the river's most enduring literary mark. Thoreau used the journey as both a physical record and a philosophical meditation, and in it he offered his own etymology for the river's name, suggesting it means "Sturgeon River." The book became an early American literary classic and ensured the Merrimack's place in the national imagination well beyond its regional role.

  Anya Seton's historical novel Avalon includes a section depicting the fictional Pre-Columbian arrival of ninth-century Irish and English travelers at the Merrimack and their interactions with local Native Americans, weaving the river into a speculative pre-contact narrative. On a different register, Mandy Moore, a native of Nashua, New Hampshire, featured a song titled "Merrimack River" along with an instrumental reprise on her 2009 album Amanda Leigh. Several US naval ships have also carried the river's name, spelled as USS Merrimac, extending its reach into American military history. In 2016, the American Rivers nonprofit named the Merrimack one of the most endangered rivers in the United States, a designation that brought fresh political pressure on the EPA to reassess a permit allowing landfill water to be discharged into the river.