The first Earth Day was celebrated on April 22, 1970, and it heralded a new era in the US. The New Yorker’s Elizabeth Kolbert explains:

Among those who seemed unmoved was President Richard Nixon. He avoided the festivities and made no public comment on them. (One of his aides, John Whitaker, later acknowledged that the Administration had been “totally unprepared” for the wave of environmental activism “that was about to engulf us.”) Nevertheless, even Nixon seems to have got the message. Three months afterward, he created the Environmental Protection Agency and the National Oceanic and Atmospheric Administration, and five months after that he signed the Clean Air Act. The Clean Water Act, the Pesticide Control Act, the Endangered Species Act, and the Safe Drinking Water Act all became law by the end of 1974.

Ten months before that first Earth Day celebration, the heavily polluted Cuyahoga River caught fire, providing a vivid example of just how bad pollution had gotten and helping to galvanize a nascent environmental movement that pushed for new environmental legislation. Thanks to the Clean Water Act, researchers now count more than three dozen fish species in the segment of that river running between Akron and Cleveland.

It’s hard to think of a visual image of today’s environmental problems that has such a visceral impact. Many communities watch their river levels dropping, and animal lovers sigh over videos of polar bears struggling to stay afloat on melting Arctic ice. What will rally today’s crowds to demand the kind of groundbreaking legislation that followed the first Earth Day?