Nelson originally envisioned a one-time celebration and teach-in, but young activists led by then-Stanford student body president Denis Hayes decided to keep the momentum going after April 22.
"About two weeks later, the kids put an ad in the paper," McCloskey recalled. "And they said, 'We are listing the Dirty Dozen, 12 members of the House of Representatives, and we are going to defeat them in the elections.' And everyone laughed and said, 'Well, that's a bunch of kids.'"
The laughter was muted by November, when seven of those 12 representatives -- two Democrats and five Republicans -- had lost their seats. McCloskey said it was the beginning of a green wave in American government.
"In those next four years, 1971 through 1974, we enacted all the great landmark legislation. The Clean Water Act, the Clean Air Act, Endangered Species Act, marine mammals, coastal zone, estuaries protection," McCloskey said.
"It was a great heyday for environmental legislation, and it was all bipartisan. We had a Republican president (Richard Nixon), he created the Environmental Protection Agency. A wonderful Wall Street guy named Dan Lufkin helped raise the money for Earth Day, along with Sid Howe, head of the Conservation Foundation," he said.
"These were business leaders who recognized that the enjoyment of the environment and the earth was part of having a successful business," he added.
McCloskey, who is now 89 years old, left Congress in 1983 to return to the practice of law. In 2007, he left the Republican Party.
This Earth Day, he's made a new list of legislators whose voting record on the environment he thinks qualifies them for a new Dirty Dozen -- California congressmen Kevin McCarthy, Devin Nunes, Tom McClintock, Doug LaMalfa, Jeff Denham and David Valadao.