It was part protest, part celebration, and an estimated 20 million Americans took part.
On the first Earth Day, April 22, 1970, millions of people across the U.S. went to large public rallies, listened to political speeches, took part in teach-ins, went to concerts and educational fairs, and helped to clean up their communities. Air and water pollution, nuclear testing and loss of wilderness were major concerns.
Some university students in New York City donned gas masks and smelled flowers to show not only their love of nature but also their fear of impending ecological collapse. Richard Nixon was U.S. president. The '60s were over, but the environmental movement was just finding its voice.
"It was a beautiful spring day in most of the United States, and it had a very festive quality to it," says Finis Dunaway, associate professor of history at Trent University in Peterborough, Ont. Dunaway, born in the U.S., is writing a book on the history of environmentalism.
"Partly due to its celebratory quality and universal appeal, it was something that the media gave a lot of attention to and celebrated it as a day that might bring the nation together."
Earth Day was presented then, through media images, as a "non-threatening form of politics," but despite its mainstream appeal, it was far more than simply white middle class people picking up litter, Dunaway says.
And 40 years later, he says it still has the potential to encourage individual people to take small steps to protect the environment in their daily lives.
Dunaway says Earth Day also has, over the years, gained enormous corporate support. Unfortunately, he says, it has in the process marginalized important environment issues, such as lead poisoning in inner U.S. cities. And with its focus on individual action, it puts no pressure on governments and corporations to change their ways.
As a big "feel good" day, it has been dismissed by serious environmentalists as a waste of time. "Screw Earth Day," for example, was a campaign launched last year by the green blog Grist to point out that one day is not enough. In a page on its web site about the campaign, Grist asks: "You think you can make up for a lifetime of excess in one day?"
In the past 40 years, the issues have changed, with climate change now front and centre. The type of events held on Earth Day has changed a little as well.
The year 1990 was a big one for Earth Day. Dunaway says it's when the day became institutionalized and turned into an international event. Lots of celebrities got involved to support Earth Day in the U.S. An estimated 200 million people marked the day in 141 countries.
Supposed to be a 1-day wonder
Canada also took part in Earth Day in a big way in 1990. That year, the organization Earth Day Canada was formed to mark the 20th anniversary of the first day. There were rallies in major Canadian cities, and an estimated two million Canadians took part. The issues were distinctly Canadian: acid rain, forest preservation, wildlife conservation.
"There was so much interest from such a broad section of Canadians," says Jed Goldberg, president of Earth Day Canada, in Toronto. "It was the diversity of people involved that was amazing. Don't forget that Earth Day in 1990 was supposed to be a one-day wonder."
Now, according to Goldberg, Earth Day events tend to be smaller in scale with more of an internal focus. He says workplaces, communities, parks and neighbourhoods are the venues for many events.
"Large scale mammoth events have been replaced by many smaller events," he says.
Large Earth Day events in Canada this year include an Earth Walk in Victoria and an Earth Day Festival in Hawrelak Park in Edmonton. Toronto has a Community Clean-up Day, sponsored by Mayor David Miller, two days later on Saturday.
Both Goldberg and Dunaway say the day is worthwhile.
"It's not so much about raising awareness anymore," Goldberg says. "What Earth Day is about is directing interest to tangible ways of getting involved and translating interest into action."
Dunaway was 18 years old, an undergrad student at the University of North Carolina at Chapel Hill, when Earth Day turned 20 in the U.S. He remembers thinking that the day was shallow in focus.
Too much focus on individuals
"I was young and idealistic, and I remember feeling that Earth Day in 1990 in some ways cheapened the cause. I didn't think it was going to translate into major changes beyond the day."
He also thought that too much focus on individual action and responsibility took away from governments and corporations making large scale changes.
Still, he saw the value of a day that raised environmental awareness, provided people with opportunities to show their concern, and took ideas from the environmental movement and made them popular.
Now 38, having lived in Canada for six years, Dunaway says he will spend the 40th anniversary of Earth Day celebrating the second birthday of his daughter and taking a long walk.
Two days later, on Saturday, April 25, he will follow news stories on a large national rally planned for Washington, D.C., on climate change.
"Clearly, climate change is the most talked about environment issue today. To tie it in with the 40th anniversary of Earth Day it strikes me as something that could be quite promising and productive as a strategy."