College students clean streets of NYC during historic first Earth Day protest in 1970.

Take a look back at how the environmental movement has changed since 1970.

Every year, people all around the world come together to celebrate Earth Day. This annual event is marked by lots of different activities, from parades to festivals to film festivals to running races. Earth Day events typically have one theme in common: the desire to show support for environmental issues and teach future generations about the need to protect our planet.

The First Earth Day

The very first Earth Day was celebrated on April 22, 1970. The event, which some consider to be the birth of the environmental movement, was founded by United States Senator Gaylord Nelson.

Nelson chose the April date to coincide with spring while avoiding most spring break and final exams. He hoped to appeal to college and university students for what he planned as a day of environmental learning and activism.

The Wisconsin Senator decided to create an "Earth Day" after witnessing the damage caused in 1969 by a massive oil spill in Santa Barbara, California. Inspired by the student anti-war movement, Nelson hoped that he could tap into the energy on school campuses to get kids to take notice of issues such as air and water pollution, and put environmental issues onto the national political agenda.

Interestingly, Nelson had tried to put the environment on the agenda within Congress from the moment he was elected to office in 1963. But he as repeatedly told that Americans were not concerned about environmental issues. So Nelson went straight to the American people, focusing his attention on college students. 

Group of demonstrators participating in the first annual Earth Day event, NYC, 1970.

Participants from 2,000 colleges and universities, roughly 10,000 primary and secondary schools, and hundreds of communities across the United States got together in their local communities to mark the occasion of the very first Earth Day. The event was billed as a teach-in, and event organizers focused on peaceful demonstrations that supported the environmental movement.

Almost 20 million Americans filled the streets of their local communities on that first Earth Day, demonstrating in support of environmental issues in rallies large and small all across the country. Events focused on pollution, the dangers of pesticides, oil spill damage, the loss of wilderness, and the extinction of wildlife.

Impacts of Earth Day

The first Earth Day led to the creation of the United States Environmental Protection Agency and the passage of the Clean Air, Clean Water, and Endangered Species acts. "It was a gamble," Gaylord later recalled, "but it worked."

Earth Day is now observed in 192 countries, and celebrated by billions of people around the world. Official Earth Day activities are coordinated by the nonprofit, Earth Day Network, which is chaired by the first Earth Day 1970 organizer, Denis Hayes.

Over the years, Earth Day has grown from localized grassroots efforts to a sophisticated network of environmental activism. Events can be found everywhere from tree planting activities at your local park to online Twitter parties that share information about environmental issues. In 2011, 28 million trees were planted in Afghanistan by the Earth Day Network as part of their "Plant Trees Not Bombs" campaign. In 2012, more than 100,000 people rode bikes in Beijing to raise awareness about climate change and help people learn what they could do to protect the planet.

How can you get involved? The possibilities are endless. Pick up trash in your neighborhood. Go to an Earth Day festival. Make a commitment to reduce your food waste or electricity use. Organize an event in your community. Plant a tree. Plant a garden. Help to organize a community garden. Visit a national park. Talk to your friends and family about environmental issues such as climate change, pesticide use, and pollution. Commit to campaigning for elected officials who support a clean economy.

The best part? You don't need to wait until April 22 to celebrate Earth Day. Make every day Earth Day and help to make this planet a healthy place for all of us to enjoy.