“… Just as he describes it, the Concord narrows dramatically and shallows out over a ‘yellow pebbly bottom’ as it approaches the falls in Billerica, where the Thoreaus went off on the Middlesex Canal and where Kaz and I were to rendezvous with my wife, Yolanda Whitman, in her Odyssey. To let her know that we were in Billerica and when we would be landing, Kaz produced a cell phone, waved it in the air, and said, ‘Henry David couldn’t do this!’

“In the last quarter-mile, where the river widened and was something like a pond, we homed in on a small rock island with a single tree, and a very old brick factory that had been built, above the dam, forty-one years after the Thoreaus went through. Helen Potter’s Mill Mouse Gallery was in the bricks now, Colleen Sgroi’s Gallery and Art Classes, and the law office of Margaret Loranger Sweeney. The Middlesex Canal had crossed the Concord River here, drawing from this high point the water that filled the canal to the north and to the south. In a boulder on the left bank we saw a big iron D ring. It had held one end of the canal’s ‘floating bridge,’ which supported horses hauling the commercial traffic. On Faulkner Street, the brick factory and a concrete bridge from 1930 occluded the route of the Thoreaus.

“Where the brothers entered the Merrimack, whatever is left of the three locks that took them down to the river is buried beside Advance Auto Parts, 1-800 Rent-a-Car, the Tandoori Grill, and the Asian Pacific Buffet. The remains are under the Sterling warehouse for North American Van Lines and the rails of the Boston & Maine. Across Broadway from all those historic places is Hadley Field, with its baseball diamond, its children’s playground, its skateboard park, and its low stone marker as the route of the Middlesex Canal. Coming through the park, the canal went right through the warehouse and stair-stepped down to the river.

“On September 1st at 7:50 in the morning, Mark Svenvold and I started off in a light rain, due west up the Merrimack. Starting up the Merrimack, Thoreau says, ‘We now felt as if we were fairly launched on the ocean-stream of our voyage,’ and he compares the village harbors in that reach of the river to the harbors of Venice, Syracuse, and Rhodes. The Merrimack there is a thousand feet wide and subject to the winds if not of an ocean at least of a good-sized lake. I hate fighting headwinds, so I was grateful for the calm gray overcast, the rain that diminished to mist. We would be paddling upstream about forty miles, at least twenty-five per cent of it with no help from the pooling influence of dams. Mark is six foot three, in his early forties, athletic. In this endeavor, I preferred him to his wife or, certainly, my wife. This wasn’t my first rodeo. Mark also has the high fluency and ironic humor of someone else who went up this river, long ago. He is a poet, a creative-writing professor, and the author of Elmer McCurdy, a nonfiction book in which he easily bests the challenge that his central figure is a corpse.

“Lowell, which had more than a hundred thousand people by 2003, already had twenty thousand in 2003. For Thoreau, this was not a wilderness trip; these were not the woods of Maine. It was a journey up a minor American Ruhr, partly developed and partly under construction, ever more nascent with miles north. On the riverbanks, rails were being laid as he rowed. In his book, when he calls Lowell ‘the city of spindles and Manchester of America,’ he is not referring to the ambitious village thirty miles upstream. Nor is he above a borrowed thought. In his duffel, he had John Hayward’s The New England Gazetteer (published earlier in 1839), which describes Lowell as ‘the American Manchester.’

“The red bricks of Lowell and neighboring Chelmsford had come down the Merrimack in canal boats. Mark and I passed a four-story factory in whose tall windows about half the glass was not present–an empty brick shell of a bygone New England. CHELMSFORD MILLS FOR LEASE. The Merrimack is formed in central New Hampshire by the conjunction of the Pemigewasset and the Winnepesaukee (Thoreau’s Winnepisiogee) and flows pretty much due south to the Great Bend at Chelmsford, where it turns east for Lowell and the ocean. The Thoreaus, taking their ‘nooning,’ sat on sand under an apple tree and ate wild plums ‘opposite the Glass-house village’ here at the Great Bend. Henry says that Merrimack means Sturgeon River. He doesn’t say to whom. In the Algonquian language family, the word means, variously, Deep River and Rapid Water. . . .”

—John McPhee, from the Introduction to a new edition of  “A Week on the Concord and Merrimack Rivers” by Henry David Thoreau, 1849 (Princeton Univ. Press, 2004)