On this day in history, April 22, 1970, the first Earth Day was celebrated — ushering in a host of new environmental legislation. 

The idea for the observation "Earth Day" originated with Sen. Gaylord Nelson, a Democrat from Wisconsin, who had "long been concerned about the deteriorating environment in the United States," says EarthDay.org. 

"Inspired by the student anti-war movement, Sen. Nelson wanted to infuse the energy of student anti-war protests with an emerging public consciousness about air and water pollution," the site also said.

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Seeds had been planted for paying attention to the environment almost a decade earlier, however. 

By the early 1960s, "Americans were becoming aware of the effects of pollution on the environment," notes History.com.

Earth Day New York City 1970

The peaceful protests and demonstrations drew an estimated 20 million people to the streets, parks and other parts of communities for the first-ever Earth Day in 1970.  (Santi Visalli/Getty Images)

"Rachel Carson’s 1962 bestseller ‘Silent Spring’ raised the specter of the dangerous effects of pesticides on the American countryside," that site adds. 

Later in the decade, "a 1969 fire on Cleveland's Cuyahoga River shed light on the problem of chemical waste disposal," History.com continued. 

Until then, "protecting the planet’s natural resources" was not part of the national political agenda, and the "number of activists devoted to large-scale issues such as industrial pollution was minimal."

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Nelson's original idea for Earth Day was a "teach-in" on college campuses, EarthDay.org notes.

To better appeal to everyone, regardless of political affiliation, Nelson reached across the aisle and enlisted the help of then-congressman Rep. Pete McCloskey, R-California. 

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McCloskey, "a conservation-minded Republican congressman," was appointed co-chair of the event. 

Denis Hayes, a young environmental activist, was hired to organize the planned teach-ins, says that site.

The date of April 22 was chosen as it was a weekday between spring break and final exams for most colleges.

sidewalk chalk drawings earth day

Demonstrators in New York City chalked messages on the pavement during the first Earth Day on April 20, 1970.  (Getty Images)

"Recognizing its potential to inspire all Americans, Hayes built a national staff of 85 to promote events across the land and the effort soon broadened to include a wide range of organizations, faith groups and others," says the website. 

The focus of the event shifted from teach-ins to demonstrations. 

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The day was renamed "Earth Day." 

The new name "immediately sparked national media attention, and caught on across the country," the site notes. 

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An estimated 20 million people took part in the first Earth Day demonstrations, which amounted to 10% of the U.S. population in 1970, it adds.

"There were massive coast-to-coast rallies in cities, towns and communities," says the website. 

The first Earth Day was a "rare political alignment," says the website, and found support among "Republicans and Democrats, rich and poor, urban dwellers and farmers, business and labor leaders." 

Earth Day Crowd Philadelphia

"Don't litter" was one of the messages of the first Earth Day. The slogan is seen here at an image from an Earth Day rally in Philadelphia in 1970.  (Getty Images)

Following the success of the Earth Day demonstrations, Congress began to act with measures aimed at improving the environment and reducing pollution. 

In 1970, President Richard M. Nixon "created a council in part to consider how to organize federal government programs designed to reduce pollution, so that those programs could efficiently address the goals laid out in his message on the environment," says the website of the Environmental Protection Agency (EPA).

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The EPA itself was the result of this council. It was a consolidation of the "many environmental responsibilities of the federal government under one agency," the EPA site also says. 

Earth Day Milwaukee 1970 river

College students paddled down the Milwaukee River on homemade rafts as a protest against water pollution on the first Earth Day in 1970. 

The EPA's first administrator was sworn in on Dec. 4, 1970, less than eight months after Earth Day. 

Congress then passed many laws with the intention of improving the environment, including an updated Clean Air Act and the Clean Water Act, notes that website.

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In 1990, Earth Day's 20th anniversary, the celebration became truly global in scope, as Hayes, the original coordinator, was tapped to assist with "mobilizing 200 million people in 141 countries and lifting environmental issues onto the world stage," says the Earth Day website. 

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"Earth Day 1990 gave a huge boost to recycling efforts worldwide and helped pave the way for the 1992 United Nations Earth Summit in Rio de Janeiro," the Earth Day site also says.

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