Just like folk music, political activism runs deep in Pete Seeger’s life, dating back to the New Deal era of Roosevelt. The pioneering troubadour has championed everything from the rights of migrant workers to racial equality to disarmament to the environment.

In 1966, he co-founded the Hudson River Sloop Clearwater, a nonprofit dedicated to spreading the word about rampant pollution in the Hudson River and working to restore the waterway’s delicate ecosystem.

Over the years, the organization has grown into a symbol of how grassroots movements can attract widespread support through the arts.

According to its website (clearwater.org), Clearwater “conducts environmental education, advocacy programs and celebrations,” with the expressed purpose of protecting the Hudson River, its tributaries and related water bodies.

According to Clearwater exec director Jeff Rumpf, this year’s 43rd annual Great Hudson River Revival, better known as the Clearwater Festival, represents “the passing of the banjo” in terms of the next generation of performers following in Seeger’s footsteps. In this regard, the festival will mix older acts like Arlo Guthrie, who performed at the event’s breakout year in 1969, with newer ones like Susan Tedeschi.

Each year, the fest has attracted 10,000-15,000 attendees and brought in tens of thousands of dollars for Clearwater, Rumpf says.