Earth Day was created in 1970 by U.S. Senator Gaylord Nelson from Wisconsin. The first Earth Day was held on April 22, 1970, and it marked the beginning of the modern environmental movement.

Nelson was inspired by the anti-war protests of the 1960s and wanted to bring that same energy and passion to environmental issues. He hoped to get public and political attention focused on pollution, deforestation, oil spills, and other environmental problems. It worked—over 20 million Americans participated in that first Earth Day through rallies, teach-ins, and community cleanups.

The success of that day led to real change: it helped inspire the creation of the U.S. Environmental Protection Agency (EPA) and the passage of landmark environmental laws like the Clean Air Act, Clean Water Act, and Endangered Species Act.