[4] It is also possible to decode the name Assabet in the Eastern Algonquian Loup language spoken by the Nipmuc people who lived and fished on the river prior to European settlement.

[5] Various historic maps and documents denote the river's name as Asibath, Assabeth, Asabett, Assabet, Elizbeth, Elzibeth, Elizabet, Elizabeth, Elsabeth, Elsibeth, and Isabaeth.

[8][9] The name's history is further complicated by the fact that the tributary Elizabeth Brook in present-day Stow flows into the Assabet River.

Indigenous oral histories, archaeological evidence, and European settler documents attest to historic settlements of the Nipmuc near and along the Assabet River.

[10] Nipmuc settlements on the Assabet intersected with the territories of three other related Algonquian-speaking peoples: the Massachusett, Pennacook, and Wampanoag.

Five municipal wastewater treatment plants discharge cleaned water into the Assabet River (three upstream of the Maynard gauge).

In summer months this cumulative contribution of more than 10,000,000 US gallons (38,000,000 L) per day (roughly 10 cubic feet (0.28 m3) per second) can be more than half of the river's total volume.

Seven dams powered mills: Aluminum City, Allen Street, Hudson, Gleasondale, Ben Smith, Powdermill, and Damonmill / Westvale.

The Powdermill Dam was constructed to power the American Powder Mills, a complex of 40 buildings situated on 400 acres (160 ha) along both sides of the river through the towns of Acton, Concord, Maynard, and Sudbury.

[16] They are joined by the native shrubs buttonbush, common elderberry, highbush blueberry, multiflora rose, smooth arrowwood, and sweet pepperbush.

[18] Other wildflowers present in the area include arrow arum, arrowweed, bittersweet nightshade, cardinal flower, jewelweed, joe-pye weed, pickerelweed, purple loosestrife, swamp loosestrife, swamp smartweed, sweetflag, true forget-me-not, and the poisonous water hemlock.

[20] Given the Assabet's proximity to differing habitats such as forests, pastures, fields, and marshes, a wide variety of birds live in or migrate to the area.

[21] Other species—black-capped chickadee, cedar waxwing, downy woodpecker, tufted titmouse, and white-breasted nuthatch—live near the Assabet all year round.

[21] Some bird species visible from the river inhabit primarily fields, pastures, and old buildings, including American woodcock, barn swallow, bobolink, killdeer, and song sparrow.

[26][27] Common mammals living near the Assabet include minks, muskrats, raccoons, red foxes, and white-tailed deer.

It was initially introduced in the United States in the 1870s in Cambridge, Massachusetts, followed by deliberate introduction into ponds near the Concord and Sudbury Rivers.

[35] Other invasive species in the Assabet basin include the aquatic plant European water clover[20] and the fish carp.

[26] Alewife is an anadromous species of herring found in North America, meaning it mates and is born in freshwater but lives most of its life in saltwater.

Concord was in part founded as a beaver pelt trading site between Native Americans and English colonists.

Beaver dams create wetlands which foster wildlife diversity, contribute water to underlying aquifers, and combat summer droughts.

According to the National Weather Service, "The 1927 hurricane season brought a tropical storm that swept northward across western New England on Nov. 3-4, 1927.

As its warm, humid air rose over the mountains and hills, torrential rains fell, causing severe flooding over extensive areas in virtually all of northern New England and the upper Hudson basin in New York.

The severe winter of 1935-36 had deep snowfalls and long cold snaps that iced streams and rivers solid.

The Assabet River crested at 8.94 feet (2.72 m), the highest water level measured since record keeping began in 1942.

[40] Nathaniel Hawthorne wrote in praise of the river in his collection of short stories Mosses from an Old Manse: Rowing our boat against the current, between wide meadows, we turn aside into the Assabeth.

[41]Henry David Thoreau regularly visited and often took his students, including Louisa May Alcott, on educational boat trips up the Assabet River.

[43] Thoreau reflected on the Assabet's natural sensory pleasures in his journal, contrasting them favorably against the heights of human endeavor and creation: July 10, 1852 Assabet River I wonder if any Roman emperor ever indulged in such luxury as this—of walking up and down a river in torrid weather with only a hat to shade the head.

Now we traverse a long water plan some two feet deep; now we descend into a darker river valley, where the bottom is lost sight of and the water rises to our armpits; now we go over a hard iron pan; now we stoop and go under a low bough of the Salix nigra; now we slump into soft mud amid the pads of the Nymphaea odorata, at this hour shut.