The Nashua River watershed is a tangle of Merrimack River tributaries that support lush riparian habitat in north-central Massachusetts and southern New Hampshire. What is now the town of Pepperell lies at the confluence of the Nashua and Nissitissit rivers. Indigenous people have lived in this region for at least 8,000 years, and Nipmuc, Pennacook, and Nashaway tribes valued the area for hunting, fishing, and berries. European settlers arrived in 1720 and began to farm, turning forests into field.

During the industrial revolution, paper mills and other industries grew to dominate the watershed and contributed to increased deforestation and water pollution. The runoff from factories and mills, combined with the effects of dams and culverts, reshaped and degraded the land. By the 1960s, the Nashua River was ranked by government agencies as one of the nation’s ten most polluted rivers.

It is hard to overstate how polluted the river was. An Environmental Protection Agency (EPA) report from the 1960s details the gallons of industrial dyes, discharges associated with leather tanning, tons of raw sewage, catalogs of highly toxic chemicals, and biochemical oxygen demand affecting the river. According to locals, the stink was detectable more than a mile away.