Every year, people around the world celebrate Earth Day on April 22. The first Earth Day was in 1970 with 20 million people participating. It generated support in the U.S. for the creation of the Environmental Protection Administration and led to passage of the Clean Air Act, the Water Quality Improvement Act, the Endangered Species Act, and other environmental laws.
In honor of the 50th anniversary of Earth Day, you can download this commemorative poster.