In 1965, when the Charles River Watershed Association (CRWA) was founded, the river commonly ran in colors, depending on the paint being manufactured nearby. Sewage overflows were common and outfalls discharged industrial waste. Rowers who fell into the river routinely received tetanus shots and a course of antibiotics, and as recently as 1996, though the river was no longer a palette of colors, water quality had scarcely improved. The Charles became one of the USA’s cleanest urban rivers following its transformation, the story of a small science and engineering-oriented, grassroots nonprofit watershed association and the concerted efforts of many others.